Unit 8 Revision Notes

1. Unit 8 Revision Notes

2. Unit 8 Revision Notes Certain metals can be made magnetic, allowing them to be attracted to other metals. Iron is magnetic, aluminium is not. A magnet has a magnetic field flowing around it. The magnetic field is strongest at the ends. The ends of the magnet are known as the poles.

3. Unit 8 Revision Notes An iron bar can be made magnetic by rubbing it in one direction with another magnet. A magnet can be demagnetised by heating it to red hot using a bunsen. (It does not burn.) A north pole will repel another north pole. A north pole will attract a south pole. A south pole will repel another south pole.

4. Unit 8 Revision Notes A magnetic catch can be used to keep a cupboard door closed. Doctors use strong magnets to take small pieces of metal out of people’s eyes. A compass is a magnet that can spin around, it will always point to the north. An electromagnet can be switched on and off.

5. Unit 8 Revision Notes An electromagnet is used to move metal around in scrap yards. Electromagnets are also used in electric motors, loudspeakers, electric doorbells and televisions. The magnetic field looks like this

6. Unit 8 Revision Notes The symbol for a bulb is The symbol for a battery is The symbol for a wire is

7. Unit 8 Revision Notes The symbol for a switch is The symbol for a variable resistor is The symbol for an ammeter is

8. Unit 8 Revision Notes A series circuit looks like this If the circuit is complete the bulb will light. When the circuit is complete an electric current flows around the circuit.

9. Unit 8 Revision Notes The copper wire in a circuit is a conductor, meaning that it allows electricity to flow through it. All metal objects are conductors of electricity. Objects that do not allow electricity to flow through them are called insulators. Almost all non-metal objects are insulators. Carbon is the only non-metal to conduct electricity.

10. Unit 8 Revision Notes In a series circuit all of the current flows in one direction around the circuit. If there is a break in the circuit all the bulbs in the circuit will go out.

11. Unit 8 Revision Notes A switch is a piece of metal that can be moved in and out of the circuit. When the switch is in the circuit, the circuit is complete and the bulb will light. When the switch is not in the circuit, the circuit is not complete and the bulb will not light.

12. Unit 8 Revision Notes In a parallel circuit the current breaks up and flows in more than one direction around the circuit. If one bulb is removed from the circuit the other bulb will stay lit.

13. Unit 8 Revision Notes In this circuit, if the wire is cut at point X, bulb 1 will go out but bulb 2 will stay lit. In this circuit, if the wire is cut a point Y, bulb 2 will go out but bulb 1 will stay lit. In this circuit, if the wire is cut a point Z, both bulbs will go out.

14. Unit 8 Revision Notes In this circuit, switch 3 and switch 5 must be closed to light bulb X. In this circuit, switch 4 and switch 5 must be closed to light bulb 4. In this circuit, all switches must be closed to light both bulbs at the same time.

15. Unit 8 Revision Notes Resistance is a property of a substance that prevents electricity flowing through it. Conductors have a low resistance. Insulators have a high resistance. When electricity passes through a conductor, the resistance causes the conductor to heat up.

16. Unit 8 Revision Notes A variable resistor changes the amount of resistance wire there is in a circuit. The more resistance wire, the higher the resistance and the bulb is dim. The less resistance wire, the lower the resistance and the bulb is bright. A dimmer switch has a variable resistor inside it.

17. Unit 8 Revision Notes A variable resistor changes the amount of resistance wire there is in a circuit. The more resistance wire, the higher the resistance and the lower the current flowing. The less resistance wire, the lower the resistance and the higher the current flowing. The reading on the ammeter changes depending upon the resistance being used.

18. Unit 8 Revision Notes The inside of a plug looks like this. The cord grip holds the wire in place. The fuse is a safety device, if too much current flows through a fuse it will “blow”. A table lamp needs a 3A fuse, an electric heater needs a 13 A fuse.

19. Unit 8 Revision Notes This bulb has “normal” brightness. This bulb will be bright, there are two batteries supplying the electricity.

20. Unit 8 Revision Notes This bulb has will be dull, as there are two bulbs using the electricity form one battery. This bulb will be not light as the battery are connected positive end to positive end, cancelling each other out.