Electricity

Question 1

What is double insulation?

Answer 1

1. Double insulation is when the wires are insulated and there is a plastic, insulating case.
2. It stops users from getting an electric shock by preventing the external case from becoming live.
3. Double insulated appliances don’t need to be earthed.

Question 2

Explain how earthing and fuses work and their purpose

Answer 2

1. The earth wire provides a low resistance path to the earth.
2. So there is a high current flowing through the earth wire and also the live wire .
3. This high current melts and breaks the fuse in the live wire.
4. The whole appliance is isolated.
5. The fuse protects the wiring and appliance.
6. Earthing protects the user from an electrical shock.

Question 3

Explain why circuit breakers are better than fuses

Answer 3

Circuit breakers can be reset and are also faster to isolate the appliance.

Question 4

Why does a current in a resistor cause it to change temperature?

Answer 4

1. The electrons collide with the ions that make up the resistor.
2. This gives the ions kinetic energy, which causes them to vibrate and heat up.
3. This heating effect increases the resistors resistance.

Question 5

How is the fact that resistors heat up with current used in domestic contexts?

Answer 5

1. Fuses use this heating effect to protect circuits as they melt and break when there is a surge in current.
2. Toasters uses this heating effect as they contain a coil of wire that has a very high resistance. When current passes through the coil, it heats up so much that it glows and gives off infrared radiation which cooks the bread.

Question 6

What is a series circuit and what are its advantages?

Answer 6

1. A series circuit is when components are connected in a line and there are no separate branches.
2. They are useful if you want warning that one of the components has broken or failed, as all the other components also stop working.
3. They also use less wiring than parallel circuits.
4. They are used in fairy lights.

Question 7

What is a parallel circuit and what are its advantages?

Answer 7

1. A parallel circuit is when components are connected on different branches of the wire.
2. If one component breaks, the components on other branches keep working.
3. Components can be controlled individually, using separate switches.

Question 8

How do light-dependent resistors change with light intensity?

Answer 8

As light intensity increases, resistance decreases.

Question 9

How do thermistors change with temperature?

Answer 9

As temperature increases, resistance decreases.

Question 10

What is voltage?

Answer 10

The energy transferred per unit charge passed.

Question 11

What is a volt?

Answer 11

A joule per coulomb