Additional Mains Electricity

1. The main purpose of the earth wire is:-

To prevent explosions

To prevent electric shocks

To prevent fires

To keep the appliance working

To complete the electric circuit

2. A Cathode Ray Oscilloscope(CRO) is used to show a picture of the the changing voltage in an electrical circuit. The difference between a Direct Current(dc) and an Alternating Current(ac) is:-

Dc is a flat line and ac looks like a wave

Dc looks like a wave and ac is a flat line

Dc is a line up the screen and ac is a line across the screen

Dc is a line across the screen and ac is a line up the screen

Dc is a square and ac is a circle

3. A 9.9kW shower heater is used with 220V mains. What current flows through the heater?

0.45A

4.5A

45A

210.1A

229.9A

4. What type of electrical appliance will have an earth wire connected to it?

All powerful appliances

All heating appliances

Any appliance in a plastic case

Any appliance in a wooden case

Any appliance in a metal case

5. A TV recieves 4800J of energy from 20C of charge. What is the potential difference across the TV?

240V

2400V

4820V

9600V

96000V

6. THe two key reasons why circuit breakers are used instead of fuses are:-

They work faster and they are cheaper

They work faster and they are easier to reset

They are cheaper and they are easier to reset

Fuses are expensive and it takes time to find the correct one.

Fuses can give off toxic fumes and are difficult to replace

7. A current of 12A flows through through a kettle for 5 mins while it boils some water. How much CHARGE flows through the kettle?

1.4C

17C

60C

300C

3600C

8. You have the choice of a 1A, 3A, 5A, 10A or 13A fuse. Which one would you fit to a 1250W hair dryer to work with 250V mains?

1A

3A

5A

10A

13A

The hairdryer needs 5A of current to work, the best fuse is the smallest value that is BIGGER than this current

Explanation

The hairdryer needs 5A of current to work, the best fuse is the smallest value that is BIGGER than this current

9. The earth wire has green and yellow stripes. This best reason for this choice is:-

There is no sensible colour to represent the earth.

The scientists could not agree on one colour

There were two different colours used in the previous systems

It allows colour blind people to identify the earth

The stripe looks more fashionable

10. What is the colour of the live wire and where is it connected?

Blue and connected to the Left pin

Blue and connected to the Right pin

Brown and connected to the Left pin

Brown and connected to the Right pin

Green and Yellow and connected to the Top pin