A2AS PHYS REVISED PP MayJune 2012 A2 3 Practical Techniques Session 1-2-10667

7/27/2019 A2AS PHYS REVISED PP MayJune 2012 A2 3 Practical Techniques Session 1-2-10667

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TIME

1 hour 30 minutes.

INSTRUCTIONS TO CANDIDATES

Write your Centre Number and Candidate Number in the spacesprovided at the top o this page.Turn to page 2 or urther Instructions and Inormation.

ADVANCED

General Certifcate o Education

2012

7457

Physics

Assessment Unit A2 3Practical Techniques

(Internal Assessment)

Session 1

[AY231]

TUESDAY 8 MAY, MORNING

Centre Number

71

Candidate Number

A

Y231

QuestionNumber

Marks

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1

2

3

TotalMarks


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INSTRUCTIONS TO CANDIDATES

Answerall questions in this paper. Rough work and calculations must also be done in thispaper. Except where instructed, do not describe the apparatus or experimental procedures.The Supervisor will tell you the order in which you are to answer the questions. Not morethan 30 minutes are to be spent in answering each question. You may be told to start with theexperimental tests in Section A, or with the single question in Section B.Section A consists of two experimental tests. A 28-minute period is allocated for you to usethe apparatus. Two minutes is allocated to the supervisor to prepare the station for the nextcandidate. At the end of the 30-minute period you will be instructed to move to the area setaside for your next question. Section B consists of one question in which you will be tested onaspects of planning and design.

INFORMATION FOR CANDIDATES

The total mark for this paper is 60.All questions carry 20 marks each.Figures in brackets printed down the right-hand side of pages indicate the marks awarded to

each part question.You may use an electronic calculator.


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BLANK PAGE

(Questions start overleaf)


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Section A

1 In this experiment you will investigate the oscillation of five woodenlaths about a pivot close to one end of each lath.

The aims of the experiment are:

l To obtain the period of oscillation for each lath l To use the results to plot a linear graph l To use the graph to determine the value of a constant n

Apparatus

The apparatus, with the longest lath in place, has been set up asshown in Fig. 1.1.

l

pivot

lath

Fig. 1.1

(a) Measure and record the length, l, the distance between thepivot and the end of the lath in Table 1.1. Set the lath swingingwith small amplitude oscillations. Take and record sufficient

readings to obtain an accurate value forT

, the period ofoscillation. Record your readings in Table 1.1.

Repeat the procedure for the other four laths.


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Table 1.1

l/cm T/s T2/s2

[5]

(b) The relationship between Tand l is given by Equation 1.1

T nl

g

2 Equation 1.1

where gis the acceleration o ree all, o value 981 cm s22 andn is a constant.

You are required to plot a straight line graph to enable you toind the value o the constant n.

(i) Using Equation 1.1, show that plotting a graph oT2 on thevertical axis against lon the horizontal axis gives a lineargraph.

[2]

(ii) How would the value on be ound rom the graphsuggested in (i)?

[2]

(iii) A blank column in Table 1.1 has been provided or thevalues oT2. Calculate and record the values in the table.

[1]


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(c) Plot the graph ofT2 against l on the grid ofFig. 1.2. Choosesuitable scales, plot the five points and draw the best fit line. [4]

OFP

T2/s2

Fig. 1.2


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(d) Use your graph to find a value for the constant n.

n5 [4]

(e) Show that the constant n has no unit.

[2]


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2 Introduction

In this experiment you will find the resistance of an unknown resistorP, which is joined in series with a variable resistor Q. Differentcurrents will be passed through the two resistors. The potentialdifference across each resistor and the current will be measured.

The aims of the experiment are:

l To measure current and voltages l To plot a straight line graph to obtain values of two constantsA

and B l To determine the value of the unknown resistor P.

Apparatus

You are supplied with a box which contains the two resistors

arranged as shown in Fig. 2.1. Variable resistor Q is connectedbetween the terminals X and Y and resistor P between terminals Yand Z.

X

Q

Y

Z

P

Fig. 2.1


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The circuit shown in Fig. 2.2 has been connected or you.

10VDC

mA

X

Q

Y

P

Z

M1

M2

Fig. 2.2

(a) Voltmeter M1 measures the potential dierence V1 acrossresistor Q and voltmeter M2 measures the potential dierenceV

2 across resistor P. The milliammeter measures the current Iin the circuit.

Switch on the power supply and rotate the knob o the variableresistor ully clockwise. The voltmeters M1 and M2 should read0 V and approximately 10 V respectively.

(i) With the knob o the variable resistor still ully clockwise,read the value indicated by voltmeter M2.

Record this voltage as Vo.

Vo5 V

(ii) Rotate the knob o the variable resistor slightlyanti-clockwise and record the values oI, V1 and V2 inTable 2.1.


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(c) The potential difference V2 is related to the resistance RQ byEquation 2.1

RA

VB=

2

Q Equation 2.1

where A and B are constants.

A graph ofRQ against 1/V2 will give a straight line of slopeAand intercept B.

(i) Calculate values for 1/V2 and record them in Table 2.1. [1]

(ii) Plot the graph RQ against 1/V2 on the grid ofFig. 2.3.Choose suitable scales, plot the five points and draw thebest fit line. [4]

0

0

1/V2/V1

RQ/

Fig. 2.3


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(d) (i) Use the graph you have plotted to ind the value oA.

A5 VV [2]

(ii) Why can the value oB not be obtained directly romFig. 2.3?

[1]

(iii) The value oB can still be obtained by calculation.Calculate the value oB.

B5 V [3]

(e) The resistance Rp o resistor P is equal toA/Vo. Calculate thevalue oRp and record it below.(Remember, Vo was recorded in (a)(i).)

Rp5 V [1]


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Section B

3 In this question you will plan an experiment to determine the soundabsorption coeicient o a test material.

The sound absorption coefcient a describes how efcient a

material is at absorbing sound. See Fig. 3.1.

test

material

incident sound

energy

transmitted

sound energy

x

Fig. 3.1

The amplitude o the sound wave is proportional to the energy o the

sound wave. Theory suggests that the amplitude o the transmitted

sound wave varies exponentially with test material thicknessx

according to Equation 3.1.

Ax

5Aoeax Equation 3.1

Ax is the amplitude ater passing through distancexo the test

material,Ao is the incident amplitude and a is the sound absorption

coefcient.

(a) (i) You are provided with a loudspeaker, a microphone, asignal generator, three sheets o test material o

thicknesses 4 mm, 7 mm and 15 mm and a cathode rayoscilloscope (CRO). Describe how this apparatus would bearranged to allow data to be collected that would allow thesound absorption coeicient a to be determined.

[4]


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(ii) The height o the trace on the CRO varies with theamplitude o the transmitted sound waves. Name thecontrols on the cathode ray oscilloscope that have to beadjusted to obtain a single vertical line trace that almost illsthe screen.

[2]

(iii) When using the CRO a more appropriate orm oEquation 3.1 is given by Equation 3.2.

Vx5Voe

ax Equation 3.2

Outline the steps required to determine the voltage, Vx,represented by the vertical line trace.

[3]

(b) Describe the procedure that would be ollowed to obtainsuicient readings oVxandxto plot a meaningul graph.Remember the sheets o test material have thicknesses o4 mm, 7 mm and 15 mm.

[3]


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(c) Explain how you would use your data and Equation 3.2 to

determine the sound absorption coefficienta.

[4]

(d) (i) The sound absorption coefficient depends on the frequencyof the sound. How could you adapt your experiment toinvestigate this relationship?

[2]

(ii) The sound absorption coefficient is also sensitive toenvironmental factors. Name one such factor and explainhow you would minimise its impact.

[2]

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THIS IS THE END OF THE QUESTION PAPER


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Permission to reproduce all copyright material has been applied or.In some cases, eorts to contact copyright holders may have been unsuccessul and CCEAwill be happy to rectiy any omissions o acknowledgement in uture i notifed.

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A2AS PHYS REVISED PP MayJune 2012 A2 3 Practical Techniques Session 1-2-10667