maimelatct.files.wordpress.com · Web view7/12/2017 · OR if available electrical circuit board. Method: Set up the circuit as shown below

FORMAL EXPERIMENTS

INTRODUCTION

All formal experiments have the following documents:o Instruction sheets explaining the procedure to be followed for the experimento the worksheet consisting of questions to be answered under formal conditionso The teacher’s guide with instruction sheets, worksheets and the marking guidelines

(the teachers’ guide should never be released to the learners)

The teacher should hand out the instruction sheet ONLY for the conduction of the experiment in groups

In the case where there are not sufficient apparatus, experiments can be performed in groups but if there is sufficient apparatus , smaller groups can be formed or learners can perform the experiments in pairs or individually .

Each learner should record their own data or observations individually. Each learners should have their own worksheet and answer the questions individually

under exam conditions. Teachers should only hand out worksheets to each learner once learners have all done the

experiment and are all seated and ready to answer questions If it is not possible to perform the experiment and answer the worksheet on the same date, the

data collected by learners should be kept at school by the teacher. All formal experiments should be marked, and recorded by the teacher ONLY and moderated

internally. The experiment on conservation of momentum should be conducted in term 1, assessed in

term 1 and recorded in the teachers’ record book. BUT it will be recorded for SBA in term 2 as part of the term 2 SBA marks.

The teacher should first perform the formal experiments with their own apparatus and record their own results-the results provided are only exemplar results

For the Momentum experiment, the teacher can decide to vary the masses or the distances of the trolleys for each group. In this way learners have different data to work on and this reduces the challenges of similar data for all groups.

Note: Ensure that sample results are not given to learners. If it is found that learners have these figures in their results, then it will be regarded as an irregularity, and that learner report will be awarded a zero mark

NB: Learners should work individually on all worksheets

1

FOR THE EXPERIMENTS ON ELECTRIC CIRCUTS

NOTES FOR THE TEACHER

Safety:

1. Avoid water when working with electricity, especially if a transformer is used.2. The conducting wires should be insulated to prevent any short circuit that could occur to the handler.3. Make sure the batteries do not leak, as the acid they contain may be hazardous.4. Do not touch any open ended conducting wires.5. Open all switches when changing components in a circuit.

Learners must include a drawing of their circuit diagrams.

Each group must do the experiment in the presence of the teacher.

Observations

1. It is important to measure the potential difference across the three batteries in series, since the value might not be exactly 3 x 1,5 V – the batteries might be old, they never have exactly the same potential difference, it may be different batteries with slightly different voltages, etc. So it is important to obtain the actual reading. Readings could be rounded off.

Compare results of all the groups and guide learners to the required conclusion.

2. Take the readings of the current through each resistor to ensure the exact current in each branch. The sum of the ammeter readings across both resistors should be the same/equal to as the current through the main circuit. Readings could be rounded off to arrive at a conclusion


The voltmeter readings are all the same

Readings could be rounded off to arrive at a conclusion


Interpretation /Conclusions

1. V4 = V1 = V2 = V3

The potential difference across each resistor is equal to the potential difference of the batteries and across the entire parallel connection:

2. I = I1 + I2.

The main current in a series circuit is equal to the sum of the individual currents of the parallel branches.

(If identical resistors are used then I1 = I2 )

2

In a parallel circuit the resistors divide the total current and are called current dividers.

Resistors In a parallel circuit divide the current in inverse proportion.

This is a higher order conclusion and could be pursued in the theory/ class work.

Some experimental errors might have been included, for example learners may mention that:

The voltmeters and ammeters could have been slightly miscalibrated. Use the same kind of ammeters and voltmeters. (Learners should know how to take readings before doing the experiment.)

Take readings quickly as possible to avoid overheating. Temperature affects the resistance. Avoid the error of parallax when taking readings on the meters. The same learners should take the readings on the same meters for an experiment. Controlling of human

error. Minimising errors.

3

GRADE 10

LEARNERS INSTRUCTION SHEETS AND WORKSHEETS

4

PHYSICS EXPERIMENT 1 PART 1: SERIES CONNECTIONS

INSTRUCTION SHEET

PRESCRIBED EXPERIMENTPHYSICAL SCIENCE

GRADE 10

Term 2

2012

Knowledge Area: Electricity and Magnetism

Topic: Resistors in series

AIM: To investigate the relationship, if any, between the potential differences across the resistors and

cells in a series circuit.

Apparatus:

Three 1,5 V battery cells or transformer with a 4,5 V output Battery holders 2 resistors 4 voltmeter or multimeters 1 or 2 ammeters or multimeters conducting wires switch OR if available electrical circuit board

Method:

Set up the circuit as shown below

If there are insufficient voltmeters or ammeters then they should be connected at one position and take the reading and move to another position and take the reading. Close the switch, quickly take the reading and open the switch

Series circuit

1. Connect 2 resistors, an ammeter, switch and cells in series using the conducting wires (on the electric circuit

board.)5

2. Connect the voltmeter across the three cells to obtain the potential difference of the cells (V4)

3. Connect the voltmeters parallel across each of the resistors and take readings. (V1 and V2 )

4. Connect a voltmeter across resistors R1 and R2 and take voltmeter reading (V3)

5. (Move the ammeter to different positions in the circuit / connect another ammeter on the opposite side of the

cell / between the resistors in the circuit. Note the readings on the ammeter i.e. Ia and Ib

6. Tabulate your results in the table below in row A and keep them for the next activity

Results

Potential difference

across battery / cells

(V)

V4

Potential difference across R1

(V)

V1


(V)

V2


across both

resistors

(V)

V3

Ammeter readings

(A)

A

First set of results

Ia =

Ib =

6

WORKSHEET FOR SERIES CONNECTIONS

Re write your data from the instruction sheet in the table below

Potential difference across

battery / cells

(V)

V4


(V)

V1


(V)

V2


across both resistors

(V)

V3

Ammeter readings

(A)

A


Ia =

Ib =

(6)

B

Second set of results

Ia =

Ib =

(3)

Interpretation/Conclusions:

(7) What can you conclude about the ammeter readings?

Compare the readings and / or is there a relationship between the readings? (1)

7

(8) What can you conclude about the voltmeter readings?

Compare the readings and is there a relationship between the readings? (4)

(9) Repeat the experiment using other resistors and record your results in the table in row B

(10) What are your findings/ conclusions? (2)

(11) What are the possible sources of errors? (1)

Practical skills (4)

[21]

8

PHYSICS EXPERIMENT 1 PART 2

INSTRUCTION SHEET FOR PARALLEL CONNECTIONS

PRESCRIBED EXPERIMENTPHYSICAL SCIENCE

GRADE 10

Term 2

2012

Knowledge Area: Electricity and Magnetism

Topic: Resistors in parallel

AIM: To investigate the relationship, if any, between main current in the circuit and the current through resistors in a parallel circuit.

Apparatus:

Three 1,5 V battery cells or transformer with a 4,5 V output Battery holders 2 resistors 4 voltmeter or multimeters 3 ammeter or multimeters conducting wires switch if available electrical circuit board

Method:

Set up the circuit as shown below

If there are insufficient voltmeters or ammeters then they should be connected at one position and take the reading and move to another position and take the reading. Close the switch, quickly take the reading and open the switch

Parallel circuit

9

7. Connect 2 resistors in parallel, an ammeter, switch and cells in series using the conducting wires (on the electric

circuit board.)

8. Connect the voltmeter across the three cells to obtain the potential difference of the cells i.e. V4

9. Connect the voltmeters in parallel across each of the resistors and take their readings. i.e. V1 and V2

10. Connect a voltmeter across resistors R1 and R2 combination and take the voltmeter reading V3

11. Connect ammeters in each of the parallel branches and take readings of the respective currents in each branch i.e. I 1

and I2

12. Tabulate your results in the table below in row A and keep them for the next activity

Results

Potential difference across battery/cells

(V)

V4


across R1

(V)

V1


(V)

V2



(V)

V3

Current

in R1

(A)

I1

Current

in R2

(A)

I2

Main

current

(A)

I

A

10


11

WORKSHEET FOR PARALLEL CONNECTIONS

Re write your data from the instruction sheet in the table below


(V)

V4


across R1

(V)

V1


(V)

V2



(V)

V3

Current

in R1

(A)

I1

Current

in R2

(A)

I2

Main

current

(A)

I

A


(7)

B


(3)

Interpretation/Conclusions:

(7) What can you conclude about the voltmeter readings?

Compare the readings and / or is there a relationship between the readings? (2)

(8) What can you conclude about the ammeter readings?

Compare the readings and is there a relationship between the readings? (2)

12

(9) Repeat the experiment using other resistors and record your results in the table in row B

(10) What are your findings/ conclusions? (2)

(11) What are the possible sources of errors? (1)

Practical skills (5)

[22]

13

GRADE 11


14

GRADE 11 NEWTONS LAW EXPERIMENT: OPTION 1

FORMAL EXPERIMENT 1: RELATIONSHIP BETWEEN RESULTANT FORCE AND ACCELERATION" (NEWTON”S SECCON LAW)

Instruction sheet

AIM: To determine the relationship between the resultant force acting on an object and the acceleration produced.

APPARATUS: Dynamics trolley kit

4 mass equal mass pieces

Runway

METHOD: - Set up a runaway with a trolley as shown below.

Slotted masses are

Added one at a time

barrier

Mass piece m

1. Without any mass pieces raise one end of the runaway just enough so that the trolley rolls down the incline at constant velocity. This is to compensate for friction.

2. Measure the length of the runaway that the trolley is going to move through. 3. Pass a piece of string with a mass piece m hanging on one end over a pulley. Attach the other

end to the trolley so that, when the mass is released, it causes the trolley to accelerate. Attach 3 similar mass pieces onto the trolley.

4. Using a stopwatch measure the time take for the trolley to strike the barrier from the time it is released. Do these at least 3 times per mass so that the average of the 3 times may be used.

5. Use the readings to calculate the average velocity6. The force is conveniently increased when slotted masses of m are added. Place the unused

slotted masses on the trolley. Transfer them to the slotted mass holder each time the accelerating force is increased. This ensures that the total mass experiencing acceleration remains constant throughout the experiment.

7. Repeat step for with 2, 3 and then 4 mass pieces. 8. Record results.

Data representation

∆ x Mass (kg) ∆ t (s) ∆ v

15

123

Practical skill marks (2)

WORKSHEET FOR NEWTONS LAW: OPTION 1

1. Following instruction and manipulation. (2)

Criteria marksAccurately following a sequences of written/verbal instructions.

Following a sequence of instructions including branched instructions

1

Manipulative skills include correct and safe handling of apparatus and materials

Able to use all apparatus and material correctly and safely.

1

2. What is the dependant variable for this experiment? (1)______________________________________________________________

3. What is the independent variable? (1)______________________________________________________________

4. State the variable that is kept constant. (1)______________________________________________________________

5. In point 1 under the method of your experiment, you were asked to raise the runaway. Draw a fully labelled free body diagram showing all forces acting the trolley placed on the raised runaway and use it to explain why the runaway was raised.

(4)

16

6. Why were the mass pieces placed on the trolley and then transferred to the hook? (2)

7. Data collection and interpretation

Using data collected, complete Table 1 below:

∆ x Mass (kg) Time (s) ∆ v= vf-via=

v f−vi∆t

Fnet=ma

123

(18)

Data analysis

8. Draw a graph of Fnet vs acceleration. (4)

Conclusion

9. What conclusions can be drawn from this experiment. (2)_______________________________________________________________

Total: [35]

17

INSTRUCTION SHEET FOR NEWTONS LAWS EXPERIMENT: OPTION 2 ___________________________________________________________________________

THE RELATIONSHIP BETWEEN RESULTANT FORCE AND ACCELERATION (NEWTON”S SECOND LAW)

Aim To investigate the relationship between resultant force and acceleration

Apparatus

Trolley with frictionless wheels which run on a smooth runway Ticker timer and tape Batteries or transformer for the ticker timer. 3 or 4 elastic bands of the same length A metre rule

Method:

1. Write down an investigative question for this experiment.2. Select in the ticker-timer a frequency of 25 Hz or 50Hz. Determine the period of the ticker-timer.3. Determine the time for eleven dots (10 ticks intervals)(t=n x T) where n is the number of ticks or

intervals. Example

4. Place a trolley on a runway and adjust the runway to compensate for friction on the trolley wheels (incline the runway until the trolley runs with constant velocity Fig. below).

18

5. Attach one end of an elastic band to the trolley and the other end of the elastic band to the end of the ruler. Let a partner hold on to the trolley while you stretch the elastic band until 800 mm mark on the ruler is in line with the front of the trolley. Signal your partner to release the trolley and move forward with the trolley keeping the elastic band stretched by the same amount. Practice this a few times.

6. Pass the tape trough the timer and attach it to the end of the trolley. Make sure that the tape has no slack between the trolley and the timer. Start the timer, stretch the elastic as before (800 mm) and move forward keeping the elastic band stretched by the same amount to apply a constant force.

7. At the end of the motion remove the tape from the trolley and timer. Note the frequency of the timer and mark 10 dot intervals on the tape starting close to the beginning of the tape where the dots are clearly visible.

8. Repeat activities 6 and 7 for 2, and 3 elastics bands. 9. Analyse the tape for each case (trial) to determine the acceleration and record your results in table 1.

Marks for practical skills (2)

19

NEWTONS LAW WORKSHEET FOR OPTION 2

10. Following instruction and manipulation (2).



1



1

11. Identify the following variables for this experiment: (3)

Independent variable__________________________________________________________________

Dependent variable__________________________________________________________________

Controlled variable__________________________________________________________________

12. Determine the period of the ticker time (3)

____________________________________________________________________________

13. Using reading from the ticker tape, calculate the time (2)

___________________________________________________________________

14. What are the two possible significant errors in this experiment? (1)

______________________________________________________________________

15. Data presentation and interpretation of results

Using the results obtained, complete Table 1 below: (18)

Trial Resultant force PQ vx (m.s-1) QR (m) vy (m.s-1) a (m.s-2) F/a20

Number F (number of elastic bands) (m)

1

2

3

16. Data analysis

Using the data from the table of results, plot a graph of resultant force against acceleration (4)

Conclusion

17. Write the conclusion for this experiment. (2)

TOTAL [35]

21

GRADE 11 NEWTONS LAW EXPERIMENT: OPTION 3

____________________________________________________________________________

Experiment 1 (Mechanics)

GRADE 11

FORMAL EXPERIMENT 1: "RELATIONSHIP BETWEEN RESULTANT FORCE AND ACCELERATION" (NEWTON”S SECCON LAW)

Aim: To investigate the relationship between resultant force and acceleration

Apparatus

Trolley Track for the trolleyTicker timer and tape Batteries or transformer for the ticker timer. String Pulley Thread Mass pieces.

Method

1. Mount the ticker time on the track (rail).2. Attach a carbon disc to the ticker timer.3. Connect the ticker timer to a power source supply of 6 V

4. Select in the ticker-timer the frequency (number of dots in one second) 40 Hz or 50 Hz.5. Place a trolley on a runway and adjust the runway to compensate for friction on the trolley

wheels (incline the runway until the trolley runs with constant velocity).6. Pass a piece of string with a 20 g mass hanging on one end over a pulley (figure bellow).

Attach the other end to the trolley so that, when the mass is released, it causes the trolley

22

to accelerate. Choose a length of string such that the mass does not touch the ground until the trolley nearly reaches the pulley

7. Place the unused masses provided on the trolley. You are going to transfer them to the mass holder each time the accelerating force is increased. This ensures that the total mass experiencing acceleration remains constant throughout the experiment.

8. Start the timer and release the system leaving it free to move with acceleration.9. Remove the tape and select two displacements of ten intervals each (PQ and QR) from the

starting point and measure the distance covered in each case (look the diagram below).

10.Count 5 dots of the first displacement PQ and mark with an X, count 5 dots for the second displacement QR and mark with a Y. See figure above.

11.Repeat the steps 11 and 11 but hanging masses of 40 g and 60 g respectably, transferring them from the trolley.

12.Record your observations from the experiment in a table like the one below.

Trial Numbe

r

Resultant force:

(FR=Fg=mg)

Distance PQ (m)

vx (m·s-1) Distance QR (m)

v y (m·s-

1)a (m·s-2)

1

2

3

23

Worksheet for option 3

1. Following instruction and manipulation (2)

Criteria HighAccurately following a sequences of written/verbal instructions

Following a sequence of instructions including branched instructions.

1

Manipulative skills include correct and safety handling of apparatus and materials.

Able to use all apparatus and materials correctly and safely.

1

2. Determine the period of the ticker timer. (2)

3. Calculate the time between the 10 dots. (∆ t=n×T). (2)

4. In this experiment:

a. Name the independent variable. (1)b. Name the dependent variable. (1)c. Name the control variable. (1)

5. What are possible errors that can occur in this experiment? (1)6. How can the errors be eliminated? (1)

7. Data presentation and interpretation

Record your observations from the experiment in a table like the one below. (18)

Trial Number

Resultant force:

(FR=Fg=mg)

Distance PQ (m)

vx (m·s-1) Distance QR (m)

v y (m·s-1) a (m·s-2)

1

2

3

8. Analysis of results

With the result recorded in the table plot a graph of acceleration vs. resultant force and draw the line of best fit. (4)

24

Acceleration vs. resultant force.

8. What conclusion can you draw from this experiment ? (2)

TOTAL [35]

25

GRADE 12


26

Instruction sheet 1

CONSERVATION OF MOMENTUM

Example of an instruction sheet that can be given to learners

PRESCRIBED EXPERIMENT

PHYSICAL SCIENCEGRADE 12

TERM 1Week 4 at 13 hrs

P 120: DO IN WEEK 4, BUT MARK IN TERM 2

KNOWLEDGE AREA: MECHANICSTOPIC: MOMENTUM

Aim: To verify the conservation of linear momentum. (Page 100 of CAPS)

Apparatus: Two trolleys (each having their weight written on the side), Two 1 kg mass pieces,

Runway or flat surface, 2 wooden blocks & clamps, Non-permanent marker pen, meter ruler / tape

measure

Method:

1) The apparatus should be set up as per the diagram above

2) The trolleys’ spring mechanisms should be loaded (note that only one spring loaded trolley is

needed)

3) Place the trolleys back to back against each other so that the sides with the spring

mechanisms are facing each other.

4) Use the marker and mark on the desk/runaway the position of each trolleys front wheel/ front

edges

5) Release the spring mechanism by striking it with the wooden ruler.

6) Listen very carefully as the trolleys hit the wooden blocks.

7) If two distinct sounds are heard it means the trolleys did not reach the wooden blocks at the

same time.

8) Move the trolley setup either left or right (depending on which trolley reached its’ block first so

that the trolleys will reach the blocks at the same time) and repeat instructions 5 & 6

27

9) Listen carefully

10) If it seems there is only one sound as the trolleys hit the wooden blocks it means they have

reached their wooden blocks at the same time.Measure the distances (x1 and x2) and the time

(t1 and t2 ) taken for the trolleys to hit the wooden blocks.

11) Repeat the procedure 3 times and record the average time as t1 and t2 and the average

distances as x1 and x2 in table 1 below.

Make the distance measurements from the front wheel/ front edge of trolley 1. Label these

distances as x1 and x2 note the trolleys mass as m1. [Convert SI units for mass, distance and time accordingly as indicated in the tables of data]

Trolley 1 (m1) Trolley 1 (m2)

m1

(kg)x1

(m)t1

(s)m2

(kg)x 2

(m)t2

(s)1

2

3

28

WORKSHEET 1


12) Calculate the velocities (v1 and v2) and momentum (m1v1 and m2v2) for each trolley and record

the data in Table1. Round the answers to two decimal places

13) Calculate the total momentum (m1v1 + m1v2) after the explosion and record the data in

Table 1. Round the answers to two decimal places

14) Repeat instruction 1 to 12 for different combinations of masses for trolleys 1 an 2.

Practical skills marks (5)

Data collection and analysis of results

15) What is the total momentum of the system before the explosion? (1)

16) Table 1

Trolley 1 (m1) Trolley 1 (m2) Total p after

explosion

m1 x1 t1 v1 m1v1 m2 x 2 t2 v2 m2v2 m2 v1 + m2 v2

1

2

3

1 1 1 1 1 1 1 1 1 1 2

(12)

Key:Mass of trolley 1+ load = m1

Mass of trolley 2 + load = m2

Distance for trolley 1 = x1

Distance for trolley 1 = x2

Analysis of results

17) What do you observe about the total momentum before the collision and the total momentum

after the collision? (you may round off your results) (2)

29

__________________________________________________________________

18) Explain any two sources of error in this experiment (2)

__________________________________________________________________

19) What is your observation regarding the procedure in determining the time for the

trolleys to hit the wooden blocks? (2)

______________________________________________________________________________

______________________________________________________________

20) Populate Table 2 using the data from Table 1 and do the relevant calculations . (round off

your answers to a whole number)

Table 2

m1 x1 m1x1 m2 x 2 m2x2 Summ2 x1 + m2 x2

1

2

3

1 1 1

(3)

21) Compare the calculations in the last columns of table 1 and table 2 (1)

______________________________________________________

22) Some researchers use the distance x1 and x2 as a measure of the velocities (v1 and v2) of m1

and m2. These researches therefore take the magnitude and the direction of x1 to represent

the magnitude and the direction of v1 .Similarly for x2 and v2. Do you agree with this method?

Justify your answer. (4)

_____________________________________________________

[for the memo, if the learner wrote yes, they get 1 mark and 3 marks for the correct

explanation, if they said no, the whole answer is wrong]

23) Copy table 2, label it as table 3 and amend some of the headings the headings to

provide the momentum of trolley 1 , trolley 2 and the total momentum after collision.

(2)

Conclusion23) Write down the full statement of the conservation law which is reflected by this experiment?

(2)

30

______________________________________________________________________________

______________________________________________________________________________

[35]

Instruction sheet for internal resistance

TOTAL MARKS FOR INTERNAL RESISTANCE: [ 50]

INTERNAL RESISTANCE: PART 1




KNOWLEDGE AREA: ELECRICITY AND MAGNETISMTOPIC: ELECTRIC CIRCUITS

INTRODUCTION

The term ‘lost volts’ refers to the difference between the emf and the terminal voltage. The voltage is not ‘lost’. It is the voltage across the internal resistance of the battery, but ‘lost’ for use in the external circuit.

The internal resistance of the battery can be treated just like another resistor in series in the circuit. The sum of the voltages across the external circuit plus the voltage across the internal resistance is equal to the emf:

ε = Vload + Vinternal resistance

= IRexternal + Ir

Rearrange to get : V = - rI + ε

in the form y = mx + c where m = -r

Aim: To determine the internal resistance of a battery (Part 1) page 129 CAPS

Apparatus: Battery, Ammeter Voltmeter (millimeters) Rheostat (or various resistors) Connecting wires Switch, Cell holder

Method:

1. Set up the circuit as shown below:

31

2. With the switch open, take the reading on the voltmeter and ammeter.

3. Close the switch.

4. Take readings on the voltmeter and ammeter quickly and open the switch.

5. Vary the readings of the circuit by changing the settings on the rheostat.

Close the switch and take the readings of current and potential difference. Open the switch.

6. Repeat the previous step 4 / 5 times.

7. Record the results in a suitable table (5)

32

WORKSHEET ON INTERNAL RESTANCE PART 1

INTERNAL RESISTANCE

(7) Rewrite your results in your worksheet (6)

(8) Draw a graph of potential difference. versus current in a graph paper provided (6)

(9) Calculate/determine the internal resistance of the battery from the graph (4)

(10) List possible sources of errors in this experiment (2)

(11) How can errors be minimized in this experiment (2)

(12) List a precaution before you conduct the experiment (1)

Follow up questions(13) What is the y intercept of the graph? (1)

(14) What does the y intercept represent? (1)

(15) Identify the following variable in this experiment:

15.1independent variable

15.2 dependent variable

15.3 Identify the control variable

(3)

(25)TOTAL PART 1 [30]

33

R1

V

S1

A

R2

R3

INTERNAL RESISTANCE : PART 2

INSTRUCTION SHEET FOR INTERNAL RESISTANCE PART 2




KNOWLEDGE AREA: ELECRICITY AND MAGNETISMTOPIC: ELECTRIC CIRCUITS______________________________________________________________________________

Aim: Set up a series parallel network with known resistors.

Determine the equivalent resistance using an ammeter and a voltmeter and compare with the theoretical value. (Part 2) page 129

Apparatus: (Three) 1,5 V cells, three resistors, voltmeters, ammeter, (or multimeters) conducting wires, Switches, battery holder (Circuit board if available)

Method:

1 Set up the circuit as shown in the accompanying diagram, with the switch open.

2 Close the switch and record the readings on the ammeter and voltmeter.

Open the switch.

3 Repeat the above steps once more and calculate the average of the measurements.

Marks for practical skills

(4)

4 Record your results in a suitable table (4)

34

35

WORKSHEET ON INTERNAL RESISTANCE PART 2

4 Rewrite your results in your worksheet

5 Calculate the equivalent resistance of the circuit from your results. (4)

6 Calculate the theoretical value of the equivalent resistance from the given data (5)

7 Compare the results obtained in 5 and 6 above. Give any reason for the difference in

values.

(1)

Follow up questions8 Calculate the percentage accuracy of your experimental value. (2)

Marks for practical skills (4)

TOTAL PART 2 [20]

36

GRADE 10

TEACHERS MARKING GUIDELINES AND SAMPLE RESULTS

37

MARKING GUIDELINE: SERIES CONNECTIONS

Potential difference across

battery / cells

(V)

V4


(V)

V1


(V)

V2



(V)

V3

Ammeter readings

(A)

A


Ia =

Ib =

(6)

B


Ia =

Ib =

(6/2)

=3

Values with correct units e.g. 215 mA and 2 V

(7) They are the same Ia = Ib (1)

The current is constant at all places in the circuit.

(8) V4 = V3

V3 = V1 + V2

V4 = V1 +V2

The sum of the potential differences (voltmeter readings) across all the resistors in a series circuit is equal to the potential differences (voltmeter reading) across the battery.

(4)

38

(9) Refer to table

(10) The conclusions are the same (2)

(11) The circuit heats (1)

Practical skills

Setting up of circuit [4]

Cells and switch (1)

4 voltmeters with correct polarity (2)

Ammeter(s) with correct polarity (1)

Each group’s circuit must be checked during the practical

[21]

MARKING GUIDELINE FOR PARALLEL CONNECTIONS


(V)

V4


across R1

(V)

V1


(V)

V2



(V)

V3

Current

in R1

(A)

I1

Current

in R2

(A)

I2

Main

current

(A)

I

A


(7)

B


(3)

Values with correct units e.g. 215 mA and 2 V

39

(7) They are the same V4 = V1 = V2 = V3 (2)

The potential difference across each resistor is equal to the potential difference of the batteries and across the entire parallel connection:

(8) I = I1 + I2.

The main current in a series circuit is equal to the sum of the individual currents of the parallel branches.

(2)

(9) Refer to table

(10) The conclusions are the same (2)

(11) The circuit heats (1)

Practical skills

Setting up of circuit [5]

Cells and switch (1)

4 voltmeters with correct polarity (2)

Ammeter(s) with correct polarity (2)

Each group’s results must be checked during the practical

[22]

40

GRADE 11


41

MARKING GUIDELINES FOR NEWTONS LAW EXPERIMENT: OPTION 1

1. Following instruction and manipulation (2)



1



1

2. acceleration3. Resultant force4. Mass 5.

Normal(kinetic) friction

wǁ N

fr

w ꓕ weight

The runway is raised to compensate for friction so that the parallel component of weight equals and opposes the kinetic friction. Whatever force is now applied to the trolley will now become the resultant force.

6. To ensure that the mass of the entire system remains constant. a.b. Data presentation and interpretation

∆ x Mass (kg) Time (s) ∆ v= vf-via=

v f−vi∆t

F=ma

1 2 3

42

c. Data analysis

Heading for graph

x-axis and y axis labelled with units

correct scale and points plotted

line of best fit through origin

Example of a graph

0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.650

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

Acceleration vs. Net force

FR (N)

a (m·s-2)

Conclusion

9. The acceleration of the trolley is directly proportional to the resultant force

Total: [35]

43

MARKING GUIDELINE EXPERIMENT 1 : OPTION 2

Following instruction and manipulation (2).



1



1

2.

Independent: net force Dependent: acceleration Controlled: mass of the object

3. To determine the period of the ticker timer

T= 1f OR

T= 140

T=0 ,025

s4. To determine the time

t= n x T ORt= 10 x 0,025 st= 0,25 s

5. Using elastic bands of different width and length/not stretching elastic bands to the same lengthNot minimizing friction

6. Data presentation and interpretation.

Trial Number

Resultant force F (number of elastic bands)

PQ(m)

vx (m.s-1) QR (m) vy (m.s-1) a (m.s-2) F/a

1 1

2 2

44

T=1f

T= 150

T=0 ,02

s

t= n x Tt= 10 x 0,02 st= 0,2 s

3 3

7. Marking criteria for the graph

Criteria MarkF axis correctly identified(in x direction) with label and unit a axis correctly identified with label (in y direction) and unit Plotting correctly done Correct shape (straight line)

Example of a graph from the data in the table

0 0.5 1 1.5 2 2.5 3 3.50

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

F (N)

a (m

.s-2)

8. Conclusion When the mass of an object is constant the acceleration of it is directly proportional to the force that produces it.

TOTAL [35]

SAMPLE RESULTS FOR NEWTONS LAWS EXPERIMEN: OPTION 2

Tape Resultant force/

PQ

(m)

vx (m.s-1) QR (m) vy (m.s-1) a ((m.s-2) F/a

1 1 0,064 0,16 0,100 0,25 0,225 4,44

2 2 0,132 0,33 0,204 0,51 0,45 4,44

3 3 0,190 0,48 0,298 0,75 0,675 4.44

45

MARKING GUIDELINE FOR NEWTONS LAW OPTION 3

1. Actual performance of the experiment

Following the instruction and manipulation (2)

Criteria HighAccurately following a sequences of written/verbal instructions

Following a sequence of instructions including branched instructions.

1

Manipulative skills include correct and safety handling of apparatus and materials.

Able to use all apparatus and materials correctly and safely.

1

2) T=1f= 150

=0,02 s

3) ∆ t=n×T=(10 ) (0,02 )=0,2 s

4.1. Mass

4. 2 Acceleration

4.3 Force

5. Friction should be reduced drastically to almost 0

6. Put oil in the wheels of the trolley

7. Data presentation and interpretation

Trial Resultant force:

(FR=Fg=mg)

PQ (m) vx (m·s-1) QR (m) v y (m·s-1) a (m·s-2)

1

2

3

46

9. Interpretation of results

0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.650

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

Acceleration vs. Net force

FR (N)

a (m·s-2)

Criteria MarkF axis correctly identified(in x direction) with label and unit a axis correctly identified with label (in y direction) and unit Plotting correctly done Correct shape (straight line)

9. When the mass of an object is constant the acceleration of it is directly proportional

to the force that produces it. (2)

TOTAL [35]

Sample results for Newton’s law Experiment: Option 3

Trial Resultant force:

(FR=Fg=mg)

PQ (m) vx (m·s-1) QR (m) v y (m·s-1) a (m·s-2)

1 FR1=mgFR1=0,02×9,8FR1=0,196N

0,037vX=

PQ∆ t

vX=0,0370,2

vX=0,185

0,042vY=

QR∆ t

vY=0,0420,2

vY=0,21

a=v y−vx

∆ t

¿ 0,21−0,1850,2

¿0,125

47

2 FR2=mgFR2=0,04×9,8FR2=0,392N

0,036vX=

PQ∆ t

vX=0,0360,2

vX=0,18

0,046vY=

QR∆ t

vY=0,0460,2

vY=0,23

a=v y−vx

∆ t

¿ 0,23−0,180,2

¿0,25

3 FR3=mgFR3=0,06×9,8FR3=0,588N

0,056vX=

PQ∆ t

vX=0,0560,2

vX=0,28

0,07vY=

QR∆ t

vY=0,070,2

vY=0,35

a=v y−vx

∆ t

¿ 0,35−0,280,2

¿0,35

GRADE 12


48


Marking guideline: conservation of Momentum

Assessment of practical aspects:Rubric for practical skills

Bumpers and

trolleys set up to

affect motion in a

straight line

Experiment

carried out on

clean ,

smooth

surface / track

Trolleys

released

simultaneously

Initial positions

of trolleys are

correct

Positive and

negative

displacements

recorded

correctly in m

(5)

RESULTS:

15) The total momentum before collision is equal to zero (2)

Table 1

Trolley 1 (m1) Trolley 1 (m2) Totalp after

explosion

m1

(kg)x1

(m)t1

(s)v1

(m.s-1)m1v1

(kg. m. s-1)

m2

(kg)

x 2

(m)t2

(s)v2

(m.s-1)m2v2

(kg. m. s-1)m2 v1 +

m2 v2

1

2

3

49

(12)

16) The total momentum before collision is equal to the total momentum after collision [note to the

teacher: since there may be experimental errors in the experiment allow an error range of ±0,05

(2)

17) Errors in the experiment are : reaction time of the data collector/observer, if friction is not

eliminated

(2)

18) Different people have different reaction times when they hear the explosion and when they

hear/see (you see before you hear because light travels faster than sound) the trolleys hitting

the barrier. This will affect the time the time to start the stop watch and the time to stop

watch/ cell phone [many cell phones use the time of up to 2 decimal places]/ any timing devise.

(2)

19)

m1

(kg)x1

(m)m1x1

(kg.m)m2

(kg)x 2

(m)m2x2

(kg.m)Sum

m2 x1 + m2 x2

1

2

3

(3)

20) They are almost the same. (1)

21) Yes.

Applying the law of conservation of momentum and using equations of motion demonstrate (mathematically) that these positions can be taken as measures of the respective velocities.

In this experiment all the forces are internal and so the net external force is 0.

∑ F ext=0 Then the change in momentum is equal to 0. ∆ pnet=0 pTf− pTi=0 pTi= pTf

Here is important to know that the system is the two trolleys. So the total momentum before the explosion is the adding of the momentum of trolley 1 plus the momentum of trolley 2. Same happen after the explosion.

pi1+ p i2= p f 1+ pf 2m1 vi 1+m2 v i2=m1 v f 1+m2 v f 2 The trolleys start from rest so the initial velocity is 0.

50

0=m1 vf 1+m2 vf 2 After the explosion the trolleys will be moving in opposite direction so one of the velocities will be negative.

0=m1 vf 1−m2 vf 2 m1 v f 1=m2 v f 2

We can consider that v=∆ x∆ t but x i=0 so v=

x∆ t

Now:

m11

x1∆t

=m2

1x2∆t

Note that ∆ t 1=∆t 2

So: m1 x1=m2 x2 (4)

Trolley 1 (m1) Trolley 1 (m2) Net momentum

Total mass (kg)

Distancev1

(m)

Momentumm1 v1

(kg. m. s-1)

Total mass (kg)

Distancev 2

(m)

Momentumm2 v2

(kg. m. s-1)

Headings & units

1

2

3

(4)

23. The total (linear) momentum remains constant/is conserved in an isolated/a closed system/the absence of external forces. (2)

Total [35]

51

SAMPLE RESULTS FOR THE MOMENTUM EXPERIMENT


RESULTS:Sample 1


Total mass (kg)

Distancex1

(m)

Momentumm1 v1

(kg. m. s-1)

Total mass (kg)

Distancex 2

(m)

Momentumm2 v2

(kg. m. s-1)(kg. m. s-1)

1 0,598 0,575 - 0,344 0,588 0,578 0,339- 0,005 ≈

0

2 1,188 0,409 -0,486 0,588 0,743 0,437- 0,049

≈ 0

3 1,778 0,619 - 1,100 0,588 1,938 1,139+ 0,039

≈ 0

Sample 2


Total mass (kg)

Distancex1

(m)

Momentumm1 v1

(kg. m. s-1)

Total mass (kg)

Distancex 2

(m)

Momentumm2 v2

(kg. m. s-1)(kg. m. s-1)

1 1,1 0,390 - 0,429 1,1 0,390 0,429 0

2 2,1 0,256 - 0,538 1,1 0,527 0,580 +0,042

≈ 0

3 3,3 0,180 - 0,594 1,1 0,618 0,680+ 0,086

≈ 0

52

MARKING GUIDELINE FOR INTERNAL RESISTANCE : PART 1

7 Record results in a table with correct labels and units

V (V) I (A) 1,5 0 1,1 0,5 0,8 0,7 0,65 1

Headings with correct units at least 4 readings

1 mark per each set of readings(5)

8 Draw graph of results (USE ACTUAL DATA)(This is just a rough diagram)

Graph of potential difference (across battery) versus current (through circuit)

Heading: Correct labels: (1 per axis)Shape: Y-intercept:

(6)

9 Slope gives the calculation

m = ∆ y∆x =

∆V∆ I = -

1,5−0,650−1 = - 0,85 Ω r =0,85 Ω

(4)

10 Heating of the battery /circuit [Reading not taken accurately (analogue meters) 2

11 The readings must be taken quickly to avoid heating of the battery/ circuit Avoid the error of parallax 2

12 Do not conduct the experiment with wet hands. (1)

13 1,5 V (1)

14 The emf of the cell (1)

15 15.1 Independent variable: Potential difference15.2 Dependent variable: Current15.3 Control variable : Temperature/ using the same cell

(3)

(25)

53

1,5

0.65

1

V (V)

I (A)

Practical skillsCheck the circuits before the beginning the experimentammeter:(connected in series, correct polarity and to take readings by using a suitable scale/ range)

(1)

voltmeter:(connected in parallel across battery, correct polarity take readings by using a suitable scale/ range)

(1)

Rheostat:(Depending on the type of rheostat. Rheostat not to be used as a fixed resistor)

(1)

During practicalReadings are taken quickly Readings are taken accurately. (avoid the error of parallax, for analogue meters) Ordigital meters- use the correct settings (DC amps /V) and connect to correct red and black jacks

(2)

(5)

TOTAL[30]

Sample graphical representation : part 1

54

MARKING GUODELINE FOR INTERNAL RESISTANCE: PART 2

4Record results in a table with correct labels and units

V (V) I (A) 3,0 0,100 3,1 0,100

avg 3,05 0,100


1 mark per each set of readings

1 mark for the average readings

(4)

5 By experiment/ measurement

Rext = V = 3,05 = 30,5 Ω

I 0,1

(4)

6

Theoretical

1R p

= 1R1

+ 1R2

=

110

+ 115

∴Rp = 6 Ω

Rext = Rp + R1

= 6 + 22 = 28 Ω

(5)

7 Sources of errors:

accuracy of the meters, if possible use digital multi-meters, error of parallax, zero error on meters, the wires / resistors heat up resistance of connecting wires is not negligible any 1

(1)

8 % accuracy = experimental Rext x 100 = 30,05 x 100 = 108,9 9 % error

theoretical Rext 28(2)

Total (16)

Practical skillsCheck the circuits before the beginning the experiment

ammeter:(connected in series, correct polarity and to take readings by using a suitable scale/ range)

(1)

voltmeter:(connected in parallel across battery, correct polarity take readings by using a suitable scale/ range)

(1)

During practical

Readings are taken quickly Readings are taken accurately. (avoid the error of parallax, for analogue meters) Ordigital meters- use the correct settings (DC amps /V) and connect to correct red and black jacks

(2)

[20]

GRAND TOTAL INTERNAL RESISTANCE PART 1 AND PART 2 [50]

55

PROJECTS

56

PHYSICAL SCIENCES PROJECTS

INTRODUCTION

Physical Sciences investigate physical and chemical phenomena. This is done through scientific inquiry,

application of scientific models, theories and laws in order to explain and predict events in the physical

environment.

One of the purposes of Physical Sciences is to equip learners with investigative skills relating to physical

and chemical phenomena. Some of the skills that are relevant for the study of Physical Sciences are

classifying, communicating, measuring, designing and investigation, drawing and evaluating conclusions,

formulating models, hypothesising, identifying and controlling variables, inferring, observing and

comparing , interpreting, problem solving and reflective skills.

Practical work will contribute to the development of these skills. Practical work refers to practical

demonstrations, experiments and projects. Practical investigations and experiments should focus on the

practical aspects and the process skills required for scientific inquiry and problem solving.

The difference between practical investigation and an experiment is that an experiment is conducted to

verify or test a known theory whereas an investigation is an experiment that is conducted to test a

hypothesis i.e. the result or outcome is not known beforehand. During an investigation the scientific method

must be applied.

DEVELOPMENT

Scientific method refers to a set of techniques for investigating phenomena, acquiring new knowledge, or

correcting and integrating previous knowledge.

The scientific method helps scientists to create credible investigations that are sustained by reliable

evidence.

The scientific method is a logical and rational order of steps by which scientists come to conclusions about

the world around them. The scientific method helps to organize thoughts and procedures so that

scientists can be confident in the answers they find. Scientists use observations, hypotheses, and

deductions to make these conclusions. You will use the scientific method in your science projects. You

will think through various possibilities using the Scientific Method to eventually obtain an answer to your

original question.

STEPS OF THE SCIENTIFIC METHOD Observation Formulating an investigative question from the observation Formulating the hypothesis Testing of the hypothesis. This refers to the designing of the experiment to find out if the

hypothesis is true or not. Result Conclusions. This is a report that includes what has been learnt during the investigation.

57

The observation is the first step that tells you how to go about your research. This step could also be

called "research." It is the first stage in understanding the problem you have chosen. After deciding on your

area of investigation and the specific question you want to ask, you need to research all the information you

can find about the problem. You can collect information on your science topic from your own experiences,

books, the internet, or even smaller related experiments. This initial research should play a big part in the

science topic that you finally choose.

Let's take the example of the tomatoes in the garden. You notice that some tomatoes in a garden are bigger than others and wonder why. Due to this personal experience and an interest in the problem, you decide to learn more about what makes plants grow. For this stage of the scientific method, it's important to use as many sources as you can find. The more

information you have on your science project topic, the better the design of your experiment is going to be.

Also try to get information from your teachers, librarians and professionals who know the content of your

science topic. They can assist and guide you to methodical experimental setup.

An investigative question is a scientific question about the relationship between two variables. This can

be written as a question you want to answer or a problem you want to solve e.g. Does the amount of sunlight, a tomato plant receives, affect the size of the tomatoes?

A hypothesis is a statement relating two variables. It is the anticipated answer to the investigative

question. This can be written as a guess that can be tested or a prediction that will answer the question or

solve the problem e.g. The more sunlight a tomato plant receives, the larger the tomatoes will grow.

Method (Procedure)List all the variables that can affect your result.

Decide which is the independent and dependent variables are.

Decide how you will control all other variables to make your test fair.

Write down the steps of the investigation in the correct order.

Make a list of the apparatus, materials, chemicals and other equipment you will need.

Decide what you will measure and how you will record your results.

A relationship is investigated between two variables.

Independent variable is the variable that may be chosen and manipulated directly by the researcher. This

is usually plotted on the x- axis of the graph.

e.g. brightness of the light (in sample1 called experimental group) .Dependent variable: is the variable that depends on the independent variable, it changes as a result of the

change in the independent variable and it is usually plotted on the y –axis of the coordinate system. e.g.

size of the tomatoes.

Controlled variables: Refers to all other variables (factors) that must be kept constant as not to affect the

outcome of the investigation.

58

When you design your science experiment, you have to keep as many factors as possible identical

(constant) e.g. amount of water, amount of fertiliser in sample #2 (called control group), the size of the trays must be the same, the soil in both trays must be the same.

Carry out your investigation: Follow your plan safely; make changes where necessary.

This is the part of the scientific method that tests your hypothesis. An experiment is a tool that you design

to find out if your ideas about your topic are right or wrong.

It is absolutely necessary to design a science experiment that will accurately test your hypothesis. The

experiment is the most important part of the scientific method. It's the logical process that allows scientists

to learn about the world.

Record your results: The results are a record of your accurate observations or of the data that have been

collected. Choose the most suitable way to record yours results, for example, in a table or a list, a graph or

description.

The data gathered could be tabulated. The table has a heading. The variables are indicated with their units.

The data may be used to plot a graph. Each graph should have:

A heading

A suitable scale

Labelled axis (variables and units

Plotted point

A best fit line (straight or curve)

If the graph is a straight line passing through the origin then the variables under investigation are directly

proportional.

If the graph is a hyperbola then the variables under investigation are inversely proportional.

Conclusion: This is the final step in the scientific method. This is a summary of the experiment's results,

and how these results match up to the hypothesis. This contains the deductions made from the results. You

would include any unexpected results and give reasons for them.

You have two options when formulating the conclusions. Based on the results, you can either (1) you CAN

REJECT the hypothesis, or (2) you ACCEPT the hypothesis.

If your original hypothesis didn't match up with the final results of your experiment, don't change the

hypothesis. Instead, try to explain what might have been wrong with your original hypothesis. What

information did you not have originally that caused you to be wrong in your prediction? What are the

reasons that the hypothesis and experimental results didn't match up?

PROJECTA science project is an investigation that is designed to solve a problem or answer a question. It is a

“science” project because learners use a procedure called the scientific method to answer the question.

59

As part of formal assessment learners must do a project. A project for grade 10, with effect from 2012, will entail one of the following.

(1) Constructing of a device e.g. electric motor

(2) Building a physical model in order to solve a challenge you have identified using concepts in the

FET Physical Sciences curriculum

(3) Practical investigation

MAKING OF A POSTER

Posters are used in academe to promote and explain research work. They are typically shown during

conferences, either as a complement to a talk show or scientific paper, or a publication. They are of lesser

importance than actual articles, but they can be a good introduction to a new piece of research before the

paper is published.

A poster is simply a static, visual medium (usually of the paper and board variety) that you use to

communicate ideas and messages. The purpose of a research poster is to present information on research

done.

Poster formatThe recommended size of a scientific poster is 130 cm x 90 cm (height x width).

Poster layout Typically, use 3 to 5 columns

Arrange material vertically from top left corner to bottom right corner

This makes it easier for people to read, without having to move back and forth.

Sketch your layout before you start

Title

Introduction

Conclusion

Poster contentSuggested structure of a scientific poster.

Summary/abstract

Introduction (background, purpose/aims, question, hypothesis)

Materials and methods

Results

Discussion

Conclusions

Limitations

60

Bibliography/References

Acknowledgments

Focus on the main aspects of your research work and illustrate these clearly.

Do not try to add too much information to your poster as it may reduce the clarity of your presentation.

Only include relevant information on the poster that will be illustrated during your presentation.

61

GRADE 11 PHYSIC PRACTICAL INVESTIGATIONS: OPTION 1

TOTAL: 45

Instructions

In this experiment you are going to determine the coefficient of static friction between various surfaces by making use of a block sliding down an inclined plane.

A diagram of the experimental setup.

1. Answer the pre-practical questions as part of your homework before doing the practical.*2. Set up the apparatus according to the diagram above. 3. Slowly increase the height h until the wooden block just begins to move. Measure this

height. Repeat this procedure five times to determine an average height.4. Use the height and length of the plank to determine θc (the critical angle at which the

wooden block will just begin to move).5. Hence determine μs using μs=tan θc.6. Complete steps 2 – 5 for all the different surfaces you will be investigating.7. Tabulate your measurements for h ,θc and μs in Table 1. Remember to give your table a

heading as well as headings for your columns (with units).8. Draw a bar graph of the coefficients of static friction for each block covering in Figure 2.

Remember to provide a suitable heading referring to both your independent and dependent variables as well as a context or purpose and labels for your axes (with units).

9. Answer the guiding questions that fall under the heading ‘Analysis and Discussion’.10. Write down a short conclusion highlighting what was revealed in this experiment.

62

Coefficient of Static Friction

θ

h d

m

*Watch the first 12 minutes of the MIT Lecture on Friction and Objects on Slopes. You will find the pre-practical questions will make a lot more sense if you do!

Link on Edmodo and also available in the pupil drive (Pupil Drive/Physical Sciences/Grade 11)

URL: http://www.youtube.com/watch?v=uZGbtK2KBoY

A: Pre-Practical Questions

A wooden block rests on a plank of wood which is inclined at an angle θc to the horizontal. This angle is the critical angle before the block of wood begins to slide down the slope. In this scenario the component of gravity parallel to the slope is equal to the maximum static friction.

1. Draw a free-body diagram showing all forces acting on the wooden block.

(5)2. Write down expressions for the components of weight parallel and perpendicular to the slope. Indicate which of these is equal to the normal force.

(3)

3. What is the magnitude of the net force acting parallel to the slope?

(1)

4. Write down an equation for the net force acting parallel to the slope.

(2)

5. Use the above expression to show that μs=tan θc.

(3)6. Calculate the coefficient of static friction between the wooden block and the wooden plank if the angle at which the wooden block just begins to move is 30 °.

63

http://www.youtube.com/watch?v=uZGbtK2KBoY

(3)

B: Practical ReportExperiment to determine and compare the coefficient of static friction

between various surfaces

ResultsThe length of the plank was ______________________.

Table 1:Surfaces Investigated μs

(dimensionless)Block Covering Plank

wood

wood

wood

wood

wood

64

Figure 1:

Analysis and Discussion

1. Describe the general trends (patterns) observed in your data in words.

(2)

2. Try to explain the general trends (patterns) observed in your data by making use of relevant theory.

(2)

3. Evaluate your data in terms of the precision and reliability of your data.

(2)

65

(8)

(8)

4. What do you think the major sources of uncertainty were in this experiment?

(2)

5. Name two things that you could do to improve or extend this experiment.

(2)Conclusion

From the results of this practical we can conclude that

(2)

GRADE 11 PHYSICS PRACTICAL INVESTIGATION: OPTION 2

66

PRACTICAL INVESTIGATION (Exemplar)


TERM 3Week:27 TIME: 1 HOUR

KNOWLEDGE AREA: ELECRICITY AND MAGNETISM

TOPIC: ELECTRIC CIRCUITS __________________________________________________________________________________________________________

INSTRUCTION: Conduct the following practical investigation and answer the questions.

PRACTICAL INVESTIGATION (NO GROUP WORK)

Investigate the relationship between the current in a circuit and the increase in the number of resistors connected in parallel.

1 What is the INVESTIGATIVE QUESTION for this investigation? (2)

2 Write down an appropriate HYPOTHESIS for this investigation. (2)

3 For this investigation, identify the DEPENDENT variable. (1)

4 Write down ONE variable that the learners must CONTROL during this investigation (1)

5 Apart from the resistors, list of ANY TWO apparatus that that is required to conduct his investigation.

(2)

6 Draw a simple circuit diagram to illustrate how the apparatus is set up in order to take readings.

(3)

7 Describe, in point form, how to conduct the investigation and what readings should be taken at each step.

(3)

8 Conduct your investigation and record your results in a suitable table (2)

9 Draw a graph of your results (5)

10 What can you conclude from your graph? (2)

11 What precautions must be taken to minimise errors? (List 2) (2)

(25)

67

ELECTRIC CIRCUITS PRACTCAL INVESTIGATION: OPTION 2

PRACTICAL INVESTIGATION

TOPIC: ELECTRIC CIRCUITS


TERM 3Week:27 TIME: 1 HOUR

INSTRUCTION: Conduct the following practical investigation and answer the questions.

NAME OF LEARNER: _______________________ GRADE 11: ____ CLASS: _____

(NO GROUP WORK) ______________________________________________________________________________

Practical skills (to be assessed during the experiment)

Check the circuits before beginning the experiment ( No part marks)

1 ammeter:(connected in series, correct polarity and to take readings by using a suitable scale/ range)

(2)

During practical

2 Readings are taken quickly (1)

3Readings are taken accurately. (for analogue meters) avoid the error of parallax,OR digital meters- use the correct settings (DC amps) and connect to correct red and black jacks )

(1)

4 Connect resistors of the same value in parallel e.g. 10 Ω (1)

Total circuit [5]

68

A: Pre-Practical Questions

A wooden block rests on a plank of wood which is inclined at an angle θc to the horizontal. This angle is the critical angle before the block of wood begins to slide down the slope. In this scenario the component of gravity parallel to the slope is equal to the maximum static friction.

1. Draw a free-body diagram showing all forces acting on the wooden block.three forceslabelsscaledot representing objectangle shown OR Cartesian coordinates defined

(5)2. Write down expressions for the components of weight parallel and perpendicular to the slope. Indicate which of these is equal to the normal force.

Fg , y=Fg cosθFg , x=Fg sin θFg , y=FN (or statement in words)

(3)3. What is the magnitude of the net force acting parallel to the slope?

Fnet , x=0N (1)

4. Write down an equation for the net force acting parallel to the slope.

Fnet , x=Fg , x+f s ,max both forceswritten as a sum (2)

5. Use the above expression to show that μs=tan θc.∴Fg , x−f s , max = 0∴Fg , x=f s , max∴Fg sinθc=μsFN

∴mg sin θc=μsmgcosθc

∴sin θc=μscosθc

∴μs=tanθc

using f s , max=μsFN

dividing by mg or Fg

using tanθc=sinθc

cosθc

(all other marks accounted for in the scaffolding)(3)

6. Calculate the coefficient of static friction between the wooden block and the wooden plank if the angle at which the wooden block just begins to move is 30 °.μs=tan θc

μs=tan 30 °μs=0,58

formulasubstitutionanswer with no unit

(3)

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MARKING GUIDELINE ON COEFFICIENT OF STATIC FRICTION: OPTION 1

[17]

B: Practical ReportExperiment to determine and compare the coefficient of static friction

between various surfaces

ResultsThe length of the plank was ______________________. approximately 1 – 2 m with unit

Table 1: Raw data to calculate the coefficient of static friction for various block coverings reference to independent and dependent variables

Surfaces Investigated Height (m) θc (degrees) μs

(dimensionless)Block Covering Plank

wood

wood

wood

wood

wood

70

(8)

Data in TABLE 1

five different block coverings (including no covering)height values correctly recordedangles correctly calculated and recordedcoefficient of static friction correctly calculated and recorded

Figure 1: Values for the coefficient of static friction for various block coverings reference to independent and dependent variables

[16]

Analysis and Discussion

1. Describe the general trends (patterns) observed in your data in words.Smoother block coverings have lower coefficients of static friction.Smoother blocks have smaller heights / smaller critical angles.(and vice versa)

(2)2. Try to explain the general trends (patterns) observed in your data by making use of relevant theory.

Explaining the lower coefficient of static friction.e.g. smoother surfaces have fewer irregularities in their surface so the electrostatic forces of attraction between different surfaces will be stronger.Explaining the smaller height / smaller critical angle.e.g. because the static frictional force is smaller, the component of gravity parallel to the slope that just causes the block to start moving will be smaller as well. The component of gravity will be smaller with a smaller height / smaller angle.

(2)

3. Evaluate your data in terms of the precision and reliability of your data.

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(8)

Figure 1:

heading (reference to indep. and dep. variables as well as context / purpose)x-axis label with unity-axis label with unitkey / label shown (in addition to the overall label for the x-axis)scaleplotting

Evaluation of precisione.g. reference to the size of the spread in repeats or similarEvaluation of reliabilitye.g. taking several readings and taking an average increases reliability

(2)

4. What do you think the major sources of uncertainty were in this experiment?Any two specific sources of uncertainty such as:heights being longer than the meter rule therefore needing to estimateplank of wood not perfectly uniforminaccuracy in determining the exact point at which the block starts to slide down the slope (e.g. does ‘stop-start’ count, or must it slide all the way down?)

Do not accept anything vague such as ‘human error’ or ‘faulty equipment’. The source of uncertainty must be made clear as well as how it impacted the results.

(2)

5. Name two things that you could do to improve or extend this experiment.Any two suggestions likely to improve quality of results or extend the experiment such as:taking several height readings for each type of block covering to increase reliabilityuse measuring tape instead of a meter rule for sandpaper OR start lower down the plankuse the same side of the plank consistentlybe consistent in how the critical angle is determined

(2)ConclusionFrom the results of this practical we can conclude thatconclusion regarding the relationship between coefficient of static friction and the smoothness/roughness of the surfaceconclusion regarding the relationship between the smoothness/roughness of the surface and the height/critical angle

(2)

[12]TOTAL 45

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MARKING GUIDELINE FOR PHYSICS PRACTICS INVESTIGATIONELECTRIC CIRUITS : OPTION 2

1 ExamplesWhat is the relationship between the electric current and the number of resistors in parallel?ORHow does the electric current change when the number of resistors in parallel changes?

Checklist

Criteria for investigative question

Marks

Question that refers to dependent variable/

Question that refers to independent variable/

(2)

2 Any prediction that answers the investigative question

The current in the circuit increases as the number of resistors in parallel increase.

Checklist

Criteria for hypothesis

Marks

Statement that can be proved true or false (not an aim)

Question refers to dependent and independent variables

(2)

3 Current (1)

4 The battery must be the same/ keep emf the same /keep temperature constant (1)5

Power source / battery Connecting wires Switch Ammeter ANY TWO

(2)

6

(ANY THREE correct labels) not bulbs

(3)

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Power Source

R

S A

7 With one resistor in the circuit, close the switch and take the ammeter reading and open the switch

Connect a second resistor parallel to the first, close switch and take the ammeter reading

Repeat with 3 and 4 resistors in parallel

(3)

8Possible results Use real dataIndicate values of R that were usedRecord results in a table with correct labels and units

Number of resistors in parallel

I (A)

(1 only) (0,2)

2 0,4

3 0,55

4 0,8

Resistors should be of same values


(2)

9 Use real data. Indicate values of R that were used

Current v/s No. of resistors

Current (A)

No. of resistors

(5)

10 The current in the circuit is directly proportional to the number of resistors connected in parallel. ( no part marks)

(2)

11 Take the readings quickly (2)

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1,8

1,6

1,4

1,2

1,0

0,8

0,4

0,2

01

0,6

2 3 4 5 6 7 8 9 10

Heading Correct labels (1 per axis) Shape Best fit through 0

for analogue meters avoid the error of parallax, Or digital meters- use the correct settings (DC amps /V) and connect to correct red and black jacks

(25)

Circuit:

Check the circuits before the beginning the experiment

ammeter: (connected in series, correct polarity and to take readings by using a suitable scale/ range)

During practicalReadings are taken quickly Readings are taken accurately. (for analogue meters avoid the error of parallax,) Ordigital meters- use the correct settings (DC amps /V) and connect to correct red and black jacks

Connect resistors of the same value in parallel e.g. 10 Ω

(5)

Total [30]

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maimelatct.files.wordpress.com · Web view7/12/2017 · OR if available electrical circuit board. Method: Set up the circuit as shown below