# Technician’s List Demos

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Technician’s List Demos
Class Practical 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 Wire, Crocodile Clips, Power pack, commercial compass.

Electromagnets

Date Electromagnets Lesson Outcomes How I did Targets
Connector: (Level 4) What is an electromagnet? Suggest how you can make it. 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

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.

Investigating electromagnets

Include an iron core

Change the number of turns

Change the current move the slider to change the current

Electromagnets The strength of an electromagnet can be increased by doing three things: 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. 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

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

How can I improve on task 1?
Task 1: Review Go back to your lesson outcome grid and fill out the ‘How I did’ and the ‘Targets’ column. Lesson Outcomes How I did Targets Task 1: Level 5 Met? Partly met? Not met? How can I improve on task 1?

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. 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
12 23 38 49 60 Remember – keep the number of coils the same throughout this experiment!

Investigating an electromagnet – results 2
8 18 31 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

Investigating an electromagnet – graph 2

How can I improve on task 2?
Task 2: Review Go back to your lesson outcome grid and fill out the ‘How I did’ and the ‘Targets’ column. Lesson Outcomes How I did Targets Task 2: Level 6 Met? Partly met? Not met? How can I improve on task 2?

Using electromagnets – scrap yards
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. Task 3: Extension Keywords for Task 3: switch Current Passes Magnet Electromagnet Attracts Hammer 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.

How can I improve on task 3?
Task 3: Review Go back to your lesson outcome grid and fill out the ‘How I did’ and the ‘Targets’ column. Lesson Outcomes How I did Targets Task 3: Level 7 Met? Partly met? Not met? 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
2. Relay switch 1. Speaker

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 quiz Review 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…..

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