Transcript Date Electromagnets Lesson Outcomes Task 1:Explain how the strength of an electromagnet be varied Level 5 Task 2: Interpret the data to draw conclusions. Level 6 Task 3: Explain some.

Date
Electromagnets
Lesson Outcomes
Task 1:Explain how the
strength of an electromagnet
be varied
Level 5
Task 2: Interpret the data to
draw conclusions.
Level 6
Task 3: Explain some uses of
electromagnets.
Level 7
How I
did
Lesson 3
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.
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.
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…..
Magnet:
Solenoid:
N
S