Transcript Technician’s List Class Practical 1. Investigating Electromagnets. Per group:- Large Iron Nail, Insulated copper wire, power pack, 6 x cells with 1.5v output (please check output.

Technician’s List
Class 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.
Date
Electromagnets
Lesson Outcomes
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
How I
did
Targets
Connector:
(Level 4)
What is an
electromagnet?
Suggest how
you can make it.
BIG picture
• What skills will you be developing this
lesson?
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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.
Investigating electromagnets
8J Electromagnets
Include an iron core
8J Electromagnets
Change the number of turns
8J Electromagnets
Change the current
move the slider to
change the current
8J Electromagnets
New Information for Task 1
Electromagnets
The 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
Investigating an electromagnet
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:
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.
Keywords for Task 1:
• core
•Electric current
•Coil
•Ammeter
•Current
• Also write
• What are the IV,DV and controlled
variables in both the
investigations.
•Number of turns
•vary
Task 1: Answers
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: Review
Go back to your lesson outcome grid and fill out
the ‘How I did’ and the ‘Targets’ column.
Lesson Outcomes
Task 1:
Level 5
How I did
Met?
Partly met?
Not met?
Targets
How can I improve
on task 1?
Wind the insulated copper wire around the nail until you have 20
turns , and then connect it between the crocodile clips.
Set up the equpiment as demonstated
• 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.
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
Results
Voltage (volts)
Number of paperclips
picked up
Results
Number of coils
Number of paperclips
picked up
Investigating an electromagnet – results 1
Current (A)
0
Number of paper
clips attracted
0
1
12
2
23
3
38
4
49
5
60
Remember – keep the number of coils the same
throughout this experiment!
Investigating an electromagnet – results 2
Number of coils
Number of paper
clips attracted
0
0
20
8
40
18
60
31
80
46
Remember – keep the current the
same throughout this experiment!
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.
Investigating an electromagnet – graph 1
number of clips attracted
70
Graph to show how the current affects the
strength of an electromagnet
60
50
40
30
20
10
0
0
1
2
3
current (A)
4
5
Investigating an electromagnet – graph 2
Graph to show how the number of coils affects
the strength of an electromagnet
number of clips attracted
50
40
30
20
10
0
0
20
40
60
number of coils
80
100
Task 2: Review
Go back to your lesson outcome grid and fill out
the ‘How I did’ and the ‘Targets’ column.
Lesson Outcomes
Task 2:
Level 6
How I did
Met?
Partly met?
Not met?
Targets
How can I improve
on task 2?
New Information for Task 3
Using electromagnets – scrap yards
A large electromagnet is used in a scrap yard to
pick up and move heavy pieces of scrap metal.
What metals would
the electromagnet
attract?
What advantages
does an
electromagnet have
over a permanent
magnet?
Task 3: (Level 7)
Copy the diagram of an
electric bell and explain
how it works.
Keywords for Task 3:
• switch
•Current
•Passes
•Magnet
•Electromagnet
•Attracts
•Hammer
• Task 3: Extension
•gong
Task 3: (Level 7)
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: Answers
Task 3: Review
Go back to your lesson outcome grid and fill out
the ‘How I did’ and the ‘Targets’ column.
Lesson Outcomes
Task 3:
Level 7
How I did
Met?
Partly met?
Not met?
Targets
How can I improve
on task 3?
Using electromagnets – relay
Lifts, cars and other large electrical machines use high
currents.
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
Review
of lesson quiz
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…..