Domestic electricity - Paper 1 Flashcards

To revise domestic electricity (paper 1)

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1
Q

State the typical voltage for mains electricity?

A

230 V

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2
Q

State the frequency of mains electricity

A

50 Hz

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3
Q

Define a.c.

A

Alternating current, the electrons vibrate backwards and forwards. Mains electricity use a.c.

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4
Q

Define d.c.

A

Direct current. Electrons only flow in one direction. This is what we get from batteries

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5
Q

State the names and colours of the 3 wires found inside a cable.

A

Live wire - Brown
Neutral wire - Blue
Earth wire - Green and yellow stripes

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6
Q

Which wire can be missing from some appliances? Why?

A

Earth wire, if the appliance is plastic and you cannot get an electric shock from it.

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7
Q

State the role of the live wire

A

To carry the alternating potential difference from the supply to the component. the potential difference between the live and the earth is 230 V

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8
Q

State the role of the neutral wire

A

The neutral wire complete the circuit from the component back to the supply. The neutral wire is at or close to 0V

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9
Q

State the role of the Earth wire.

A

It is a safety wire to stop an appliance becoming live. the earth wire is at 0V as it only carries a current if there is a fault.

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10
Q

State the relationship between power, potential difference and current.

A
Power = potential difference x current
P = VI
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11
Q

State the units of power

A

Watts (W)

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12
Q

State the units of potential difference

A

Volts (V)

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13
Q

State the units of current

A

Amperes (A)

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14
Q

State the relationship between power, resistance and current.

A

Power = (Current)squared x resistance

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15
Q

State the units for resistance

A

Ohms

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16
Q

When using an electrical device what factors affect how much electrical energy it uses?

A
  1. Time it is used for

2. The power of the appliance

17
Q

State the equation between energy transferred, power and time

A

Energy transferred (J) = Power (W) x time (s)

18
Q

State the equation between energy transferred, charge and potential difference

A
Energy transferred (J) = Charge (C) x potential difference (V)
E = QV
19
Q

State the parts that make up the national grid

A

Cables, pylons, step up transformers, step down transformers

20
Q

What does a step up transformer do? Why?

A

Increases the potential difference, which decreases the current. this reduced the amount of energy lost os heat so makes them more efficient.

21
Q

What does a step down transformer do? Why?

A

Decreases the potential difference which increases the current. this makes them safer to use

22
Q

What is the casing of a plug made from? Why?

A

Plastic , it is a good insulator and strong

23
Q

What are electrical wires made from? Why?

A

Copper, ductile and a good conductor

24
Q

What are the pins in a plug made from? Why?

A

Brass, its a good conductor but also strong

25
Q

Where is the fuse in a plug?

A

Between the live pin and the live wire

26
Q

What is the role of the fuse?

A

If current gets too high the fuse melts and breaks the circuit, cutting off the live wire

27
Q

What happens when the live wire touches the case, in terms of the earth wire?

A

The large current surges down the earth wire and the fuse blows