Technician’s List
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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…..