Technician’s ListClass Practical

1. Investigating Electromagnets. Per group:- Large Iron Nail, Insulated copper wire, power pack, 6 x cells with 1.5v output (please check output before hand), rheostat, pencil, wires, crocodile clips, ammeters. Graph paper

Demos

1. Wire, Crocodile Clips, Power pack, commercial compass.

Electromagnets

Date

Lesson Outcomes How I did

Targets

Task 1: Investigate the factors which effect the strength of an electromagnet

Level 5

Task 2: Interpret the data to draw conclusions.

Level 6

Task 3: Explain some uses of electromagnets.

Level 7

Connector: (Level 4)

What is an electromagnet?

Suggest how you can make it.

BIG picture• What skills will you be developing this

lesson?• Literacy• Team work• Self management• Creative thinking• Independent enquiry • Participation• Reflection• How is this lesson relevant to every day

life? (WRL/CIT)• Uses of electromagnet, understand

how the door bell works.

Demonstration

• Pass current through a wire held next to a commercial compass. – What happens to the needle? – What does this mean?– Discuss with the person next to you for 2

minutes.

• Now turn the wire into a few turns. Pass some current through it. What happens to the needle?

Demonstration

• Make a crude electromagnet using copper wire wrapped around a pencil. Ask students to explain why this has become magnetic.

Making an electromagnet

When electricity is passed through a coil of wire, the coil has a magnetic field around it. This is called an electromagnet.

If the coil of wire is wrapped around a piece of iron, such as an iron nail, the magnetic field gets stronger.

8J ElectromagnetsInvestigating electromagnets

8J ElectromagnetsInclude an iron core

8J ElectromagnetsChange the number of turns

8J ElectromagnetsChange the current

move the slider to change the current

ElectromagnetsThe strength of an electromagnet can be increased

by doing three things:

1) Increasing the voltage

or current

2) Increasing the number of coils

3) Inserting an iron core

New Information for Task 1

An iron core at the centre of a coil of wire, increases the strength of an electromagnet.

Investigate the other factors that can affect the strength of an electromagnet:

Investigating an electromagnet

1. Investigate how the number of coils affects the number of paper clips attracted to an electromagnet .

2. Investigate how the size of the voltage affects the number of paper clips attracted to an electromagnet .

Task 1 (Level 5)• List the material/ equipment needed for the

two investigations• Explain how you are going to carry out the

investigations.• You must clearly write the aim of your

investigation.

• Also write • What are the IV,DV and controlled variables

in both the investigations.

Keywords for Task 1:

• core

•Electric current

•Coil

•Ammeter

•Current

•Number of turns

•vary

Aim: to test the effects that increasing the number of coils and the voltage will have on the strength of an electromagnet

Equipment needed:

. Low voltage DC power supply• paper clips• insulated copper wire• crocodile clips attached to wires• connecting wires x 2• iron rod (nail)

• IV; number of coils or voltage• DV strength of magnet measured by how many paperclips you can

pick up• CV. Power supply, type of wire, ammeter

Task 1: Answers

Task 1: Review

Lesson Outcomes How I did Targets

Task 1:

Level 5

Met?

Partly met?

Not met?

How can I improve on task 1?

Go back to your lesson outcome grid and fill out the ‘How I did’ and the ‘Targets’ column.

• Increasing the Voltage

1 With the iron core still inside the coil, adjust the power supply to 2V and note how many clips can be picked up.

2 Increase the current to 3 or 4V and record the number of paper clips it picks up.3 Continue to increase the voltage by 1 or2 V each time until you reach 6. Record each

of your results and then turn off the power supply.

• Increasing the number of turns

1 Set the current to 2V and see how many paper clips you can pick up.2 Increase the number of turns to 30 and repeat number 1.3 Continue to increase the number of turns from 30 to 40 then 50. Record your results

each time.

Set up the equpiment as demonstated

Wind the insulated copper wire around the nail until you have 20 turns , and then connect it between the crocodile clips.

Task 2 (Level 6)

• Task 2: Record the results in a table.

• Plot the graphs for both the experiments.

• From the graphs ,write down the conclusion

• Extension :• Suggest ways to improve

your investigation.

Keywords for Task 2:

• increases

•Decreases

•Stronger

•Electromagnet

•Number of turns

ResultsVoltage (volts) Number of paperclips

picked up

Results

Number of coils Number of paperclips picked up

Current (A) Number of paper

clips attracted

0

1

2

3

4

5

Remember – keep the number of coils the same throughout this experiment!

Investigating an electromagnet – results 1

0

12

23

38

49

60

Number of coils Number of paper

clips attracted

0

20

40

60

80

Remember – keep the current the same throughout this experiment!

Investigating an electromagnet – results 2

0

8

18

31

46

Task 2: Answers

• Result 1

• As the current is increased the electromagnet becomes stronger.

• Result 2

• If the number of coils is increased the electromagnet becomes stronger.

Graph to show how the current affects the strength of an electromagnet

0

10

20

30

40

50

60

70

0 1 2 3 4 5current (A)

nu

mb

er

of

clip

s a

ttra

cte

d

Investigating an electromagnet – graph 1

Graph to show how the number of coils affects the strength of an electromagnet

0

10

20

30

40

50

0 20 40 60 80 100number of coils

num

ber

of c

lips

attr

acte

d

Investigating an electromagnet – graph 2

Task 2: Review

Lesson Outcomes How I did Targets

Task 2:

Level 6

Met?

Partly met?

Not met?

How can I improve on task 2?

Go back to your lesson outcome grid and fill out the ‘How I did’ and the ‘Targets’ column.

What advantages does an electromagnet have over a permanent magnet?

What metals would the electromagnet attract?

A large electromagnet is used in a scrap yard to pick up and move heavy pieces of scrap metal.

Using electromagnets – scrap yards

New Information for Task 3

Task 3: (Level 7) Copy the diagram of an

electric bell and explain how it works.

• Task 3: Extension

Keywords for Task 3:

• switch

•Current

•Passes

•Magnet

•Electromagnet

•Attracts

•Hammer

•gong

A battery or direct current supply is connected to the

terminals. When the switch is closed i.e. the door

bell push switch is pushed, a ___________ flows

through the electromagnet which becomes

________ and attracts the metal bar, the armature,

pulling it towards the electromagnet. The striker hits

the bell. This causes a _________ in the circuit and

the __________ stops flowing. The electromagnet

is no longer ___________ and the spring metal

strip pulls the armature back. Contact is made, a

current ________ and this process is repeated.

Task 3: (Level 7)

Task 3: Answers

Task 3: Review

Lesson Outcomes How I did Targets

Task 3:

Level 7

Met?

Partly met?

Not met?

How can I improve on task 3?

Go back to your lesson outcome grid and fill out the ‘How I did’ and the ‘Targets’ column.

Lifts, cars and other large electrical machines use high currents.

Using electromagnets – relay

A relay, which includes an electromagnet, is used to allow a small current in one circuit to control a large current in another circuit.

Examples of electromagnets

1. Speaker 2. Relay switch

Uses of electromagnets 2 -

An electric bell

Homework

• Homework task: Draw the diagram of a relay ,explain its functioning.

• Due date:

• Criteria for level 5:

• Criteria for level 6:

• Criteria for level 7:

Multiple-choice quizReview of lesson

What Have I Learnt?• There are three type of magnets: _________, ________ and _______

• _______, ______ and ____ are magnetic metals.

• Like poles ________, unlike poles ___________.

• Magnetic forces act at a distance because of their _______ lines

• Field lines act from ________ to ________.

• The most magnetic part of magnets are the _______.

• A magnet can be made by ___ a piece of______ or rubbing it with a _____ magnet.

• A ___of wire with an _____ ____ flowing through it becomes a magnet.

• Putting _________ inside a current-carrying coil increases the ______ of the electromagnet.

• Increasing the number of ______ of wire or increasing the ______ also increases the strength of an electromagnet.

• Door _______ and _______ use electromagnets.

• Electromagnets are useful because…..