P2.4 - Mains Electricity Flashcards Preview

GCSE Physics > P2.4 - Mains Electricity > Flashcards

Flashcards in P2.4 - Mains Electricity Deck (31)
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0
Q

What is alternating current?

A

Current that repeatedly reverses its direction.

1
Q

What is direct current?

A

Current in one direction.

2
Q

What is the peak voltage of an alternating pd?

A

The maximum voltage measured from zero.

3
Q

How is the frequency of an alternating current calculated with an ocilloscope?

A

Freq. = 1 / time taken for one cycle

4
Q

What is the casing of mains electricity devices made of and why?

A

Stiff, thermosetting plastic because it is a good insulator.

5
Q

What is in a mains cable?

A

Three insulated copper wires surrounded by a plastic outer sleeve.

6
Q

What colour is the live wire?

A

Brown

7
Q

What colour is the neutral wire?

A

Blue

8
Q

What colour is the earth wire?

A

Yellow and green

9
Q

Why does a three pin plug have an earth pin?

A

So the metal case of a mains appliance is insulated.

10
Q

What are plug pins made of?

A

Brass because it is a good conductor and doesn’t rust.

11
Q

What is a fuse used for?

A

The appliance is cut off if the current is too high.

12
Q

Why is a fuse in between the live wire and pin?

A

The appliance can be cut off from the current if the fuse blows?

13
Q

What is a circuit breaker?

A

An electromagnetic switch that trips in the event of too much current passing through.

14
Q

Why aren’t appliances with plastic cases earthed?

A

Plastic is an insulator so cannot become live.

15
Q

How does a fuse work?

A

A fuse contains a thin wire that heats up and melts if too much current passes through.

16
Q

What is the rating of a fuse?

A

The maximum current that can pass through without melting the wire.

17
Q

Give three advantages of using an RCCB.

A
  • It works faster than a circuit breaker
  • It can be used where there is no earth
  • It is more sensitive.
18
Q

How does an RCCB work?

A

An RCCB trips when the current in the live wire is different to the current on the neutral wire.

19
Q

What is the relationship between power and energy?

A

The power supplied to a device is the energy transferred each second.

20
Q

What is the equation for power of an appliance?

A

Power (W) = energy transferred (J) / time (s)

21
Q

What is an electrical current?

A

The rate of flow of charge.

22
Q

How is the flow of electric charge calculated by the current?

A

Charge (Coulombs) = current (amps) x time (seconds)

23
Q

What energy transfers take place when charge flows through a resistor?

A

The energy transferred makes the resistor hot.

24
Q

How is energy transfer calculated in relation to pd and charge?

A

Energy transferred (J) = pd (V) x charge flow (C)

25
Q

What is the relationship between the electrical energy supplied by the battery and energy transferred to the components?

A

After a while, the energy supplied is equal to the energy transferred.

26
Q

Why are electrical faults dangerous?

A

They can cause electric shocks and fires.

27
Q

Give three important factors to consider when buying an electrical appliance.

A
  • Cost
  • Power rating
  • Efficiency rating
28
Q

What is the most efficient type of lightbulb?

A

Led

29
Q

What is the lifetime of an LED?

A

30,000 hours

30
Q

What is the most inefficient lightbulb?

A

Filament bulb