Mains electricity

Question 1

What is AC, and what is its current and frequency in mains electricity?

Answer 1

AC is alternating current, which repeatedly flows back & forth at 230 V with a frequency of 50 Hz in mains electricity

Question 2

What is DC?

Answer 2

DC is direct current, which only flows in one direction

Question 3

What uses AC and what uses DC?

Answer 3

• Mains electricity uses AC

- Batteries use DC

Question 4

How do you work out frequency?

Answer 4

1 divided by time period

Question 5

What do AC and DC look like on an oscilloscope?

Answer 5

• AC gives a regular repeating wave

- DC gives a flat line

Question 6

What potential hazards regarding electricity can occur in the home?

Answer 6

• Long or frayed cables
• Water near sockets
• Damaged plugs
• Cables in contact with something hot or wet
• Too many plugs in one socket
• Appliances without covers on

Question 7

What are the wires in a plug called, where are they located and what are their corresponding colours?

Answer 7

• Neutral- blue- bottom left
• Earth- green and yellow- middle
• Live- brown- bottom right

Question 8

Aside from wires, what else do you need in a plug?

Answer 8

• Fuse

- Cable grip

Question 9

What is a feature of the live wire?

Answer 9

It alternates between positive and negative voltage

Question 10

What is a feature of the neutral wire?

Answer 10

It is always at 0v

Question 11

What is the fuse?

Answer 11

A safety device which melts if too much current goes through the circuit, to break the circuit if there is a fault

Question 12

What size fuse should you always have compared to the current flowing through?

Answer 12

It should be just above the normal operating current

Question 13

What is the function of the earth wire?

Answer 13

If a fault develops when the live wire touches the metal case of an appliance, current surges down the earth wire to the ground, melting the fuse, breaking the circuit. The appliance is now isolated, preventing electrocution, fire or damage to the appliance

Question 14

What does a circuit breaker do?

Answer 14

When they detect a surge in current, they break the circuit by opening a switch

Question 15

What is an advantage and a disadvantage of a circuit breaker over a fuse?

Answer 15

• Can easily be reset after it breaks unlike a fuse, breaks circuit quicker than a fuse
• More expensive

Question 16

What is one example of a circuit breaker?

Answer 16

A Residual Current Circuit Breaker (RCCB), which can detect tiny changes in current by detecting the difference between the live and neutral wire so can cut current off very quickly

Question 17

How do you determine whether an appliance is efficient?

Answer 17

An appliance is efficient if it wastes less energy e.g. light-emitting diodes are more efficient than filament bulbs

Question 18

What happens to the electrical energy when current flows through something?

Answer 18

When a current flows through something, resistance means electrical energy is transferred into heat energy. The bigger the voltage and current, the more heat is produced

Question 19

What is potential difference?

Answer 19

Energy transferred per unit of charge

Question 20

What happens when an electrical charge goes through change in potential difference?

Answer 20

Energy is transferred

Question 21

What happens to charge at the power source?

Answer 21

At power source, energy is supplied, raising the charge through a potential

Question 22

What happens to charge at components?

Answer 22

At components, the charge gives up its energy, falling through potential

Question 23

What happens as the change in potential difference increases?

Answer 23

More energy is transferred for a given amount of charge passed through the circuit

Question 24

What effect does the size of the voltage of a battery have on energy and charge?

Answer 24

Batteries with bigger voltages will supply more energy for every coulomb of charge which flows around it because charge is raised up higher at the start and more energy will be dissipated