slide-deck.pptx electromagnet electromagnet

electromagnet

1. Electromagnets Magnets and electromagnets

2. magnetic field this exerts a force on magnets and magnetic materials core the centre of an electromagnet around which a wire is wound to make a coil electromagnet a magnet made using a coil, a core and a power supply coil a wire wound round in loops and looks like a spring turn a single loop of wire in a coil

3. An electromagnet More turns on an electromagnet Electromagnets

4. The magnetic needle of a compass is not affected by electrostatically charged objects. An electromagnet The compass needle does not move when charged objects are brought near. Magnetic and electrostatic forces are different types of force.

5. When current starts to flow through a wire, a nearby magnetic compass needle is deflected. An electromagnet When the current is turned off, the needle returns back to the original position.

6. Which of the following would not cause a compass needle to deflect? An electromagnet iron nail another magnet Earth’s magnetic field a positively charged balloon

7. An electromagnet Electric current causes a magnetic field around the wire that carries it. electric current A compass needle aligns along this field. magnetic field

8. An electromagnet If there is no electric current flowing, there is no magnetic field around the wire. no electric current no magnetic field

9. An electromagnet If more wires carry more current, there will be a stronger magnetic field.

10. Coiling the single wire is like increasing the number of wires carrying current. An electromagnet This magnetic field can be shown with a plotting compass.

11. This simulation shows the direction of the magnetic field around a current carrying coil . An electromagnet GIF from a simulation by PhET Interactive Simulations, University of Colorado Boulder, licensed under CC-BY-4.0 The field is the same shape as that of a bar magnet.

12. A plotting compass will behave the same with either a coil or a bar magnet. The field from a current carrying coil is different to that from a bar magnet. Bar magnets do not have a current flowing in them. An electromagnet

13. Placing an iron core inside the coil increases the magnetic field strength. An electromagnet iron core

14. An electromagnet can be made by winding different numbers of turns of wire in a coil around an iron core. An electromagnet iron core (rod) insulated wire power supply A power supply can provide the current.

15. Wind the wire in some turns to make a coil. An electromagnet Twist the wire together to stop the coil unravelling. Make sure the turns of the coil are all less than 2 cm from the end of the iron core.

16. When more turns are wound onto the coil, ensure these are all close to the end too. An electromagnet 2 cm 2 cm increased number of coils

17. Testing the electromagnet: An electromagnet Bring the coil near the paper clips. Switch on the power. Pick up as many paper clips as possible. Move to the side and release the paper clips by switching off the current. Count the number of paper clips picked up.

18. Why do paper clips fall off the electromagnet when the current is turned off? An electromagnet there is no charge in the wire there is no field due to the coil the electromagnet has reversed polarity

19. Build an electromagnet using an iron core, an insulated wire, a power supply (max 3 V) and test it with some paper clips. Record your results in a table. An electromagnet number of turns number of paper clips picked up 1 2 3 mean 5 10 15 20 25 When you have collected a set of results, calculate a mean and plot a graph of paper clips picked up against number of turns.

20. An electromagnet number of turns number of paper clips picked up 1 2 3 mean 5 2 4 3 3 10 5 8 8 7 15 19 20 16 18 20 30 24 39 27 25 29 33 32 31 Sample results: 39 paper clips for 20 turns was an anomalous result so it was not used in the average calculation.

21. An electromagnet An example graph:

22. An electromagnet More turns on an electromagnet Electromagnets

23. The graph from the experiment shows that increasing the number of turns on the coil, increases the number of paper clips picked up. More turns on an electromagnet The more turns there are, the stronger the magnetic field.

24. How many paper clips would be picked up if 14 turns were used on the coil? More turns on an electromagnet 13 14 15

25. How many turns are needed to pick up 10 paper clips? More turns on an electromagnet 11 12 13

26. More turns on an electromagnet A current carrying coil will have magnetic field lines passing through it. Increasing the number of turns on the coil will increase the number of magnetic field lines inside the coil.

27. Which of the following will cause a stronger magnetic field? More turns on an electromagnet increasing the current through the coil increasing the diameter of the coil increasing the number of turns on the coil increasing the resistance of the coil

28. Explain how you could make an electromagnet using an iron nail, some insulated wire and a battery. 2. Explain why the wire needs to be insulated. More turns on an electromagnet

29. More turns on an electromagnet Explain how you could make an electromagnet using an iron nail, some insulated wire and a battery. Wind the insulated wire around the end of the top of the nail. The head will help stop the coil slipping off the nail. Connect the ends of the wire to the battery. The nail will become an electromagnet. If you want to turn off the electromagnet, break the connection to the battery and there will no longer be a magnetic field.

30. More turns on an electromagnet Explain why the wire needs to be insulated. Current needs to flow around the coil to cause a magnetic field. If the wire is not insulated, the current will flow straight through the wire and the core without passing through the turns of the coil. This will not cause the strong magnetic field of an electromagnet. There will be a small field due to the current, but not one big enough to pick up paper clips.

31. A current flowing in a wire will cause a magnetic field that can be detected with a compass around the wire. Electromagnets Increasing the number of wires by coiling them will increase the magnetic field. The magnetic field due to a coil is the same as that due to a bar magnet. Adding a soft iron core to the centre of the coil, or increasing the number of turns on the coil, will increase the magnetic field and make an electromagnet stronger.