Chpt 5 - Electricity in the home

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17 Terms

1
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What is direct current (d.c.)?

A current that always flows in one direction. It is the current found in circuits powered by a cell or battery.

<p>A current that always flows in one direction. It is the current found in circuits powered by a cell or battery.</p>
2
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What is alternating current (a.c.)?

When electricity flows in alternate directions back and forth in a circuit due to an alternating potential difference. Found in mains electricity

<p>When electricity flows in alternate directions back and forth in a circuit due to an alternating potential difference. Found in mains electricity</p>
3
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Name the 3 wires in a plug

- Live
- Neutral
- Earth

<p>- Live<br>- Neutral<br>- Earth</p>
4
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What is the live wire?

Carries alternating potential difference from the supply. It is brown

<p>Carries alternating potential difference from the supply. It is brown</p>
5
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What is the neutral wire?

Completes the circuit and carries current away from the appliance (0v). It is blue

<p>Completes the circuit and carries current away from the appliance (0v). It is blue</p>
6
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What is the earth wire?

- green and yellow
- works with fuse to prevent fires and shocks
- used for safety

<p>- green and yellow<br>- works with fuse to prevent fires and shocks<br>- used for safety</p>
7
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What is a short circuit?

A connection that allows current to take the path of least resistance

8
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What is the National Grid?

A giant system of cables and transformers that covers the UK and connects power stations to consumers

<p>A giant system of cables and transformers that covers the UK and connects power stations to consumers</p>
9
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What is the potential difference of the National Grid?

230V

10
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What is the frequency of the National Grid?

50Hz

11
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What is a transformer?

A device that increases or decreases the voltage of alternating current

12
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Why is the potential difference stepped up to 40000V before it transfers through cables in the National Grid?

High potential difference means current is low. Due to low current, wires heat up less and less energy is wasted

13
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Why is the potential difference stepped down back to 230V before it enters buildings?

So it can enter buildings at a safe potential difference. Plugs in the UK are only designed to transfer electricity at 230V and 50Hz. Anything higher than that, it would be very dangerous and could cause electrical fires.

14
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Equations for power

power = current x potential difference
or
power = current² x resistance

15
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Equation for charge flow

Charge flow = current x time

16
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Equation for energy transferred to an electrical appliance

Energy transferred = charge flow x potential difference

17
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Equation for energy transferred by an electrical appliance

Energy transferred = power x time