Electricity in the home Flashcards

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1
Q

What is the National grid?

A

It is a network of cables, pylons and transformers.

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2
Q

What is the function of the National grid?

A

Its function is to deliver electricity to homes, schools, offices and factories.

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3
Q

How does the National grid do its function?

A

It does this in the most efficient way possible, that is by reducing the energy loss across cables as heat.

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4
Q

What does a step up transformer do?

A

Increases the p.d, but decreases the current; a lower current reduces heat loss.

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5
Q

What is the equation for power loss?

A

P = I^2R

Power (Watts) = Current^2 (Amps) x Resistance (Ohms)

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6
Q

What does the live wire do?

What colour is the live wire in a mains plug?

A

The electricity goes in and is transferred from the power station to the user.

Brown

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7
Q

What does the neutral wire do?

What colour is the neutral wire in a mains plug?

A

The electricity goes out and is transferred from the user to the power station.

Blue

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8
Q

Where does the earth wire go?

What colour is the earth wire in a mains plug?

A

It goes into the ground through a large conductive hole.

Yellow and green

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9
Q

Why are most of the plug and cable externally made from plastic?

A

For their insulation properties.

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10
Q

The brass pins connected to the plug are…

A

good conductors and are strong, resilient and rust resistant.

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11
Q

Inside the plug how does electricity flow through it?

A

electricity enters via the pin connected to the brown wire, and then onto the appliance. Then it is connected to the blue as the output back to the socket.

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12
Q

What does the Earth ensure if a live connection at the appliance touches the metal casing?

A

There is a surge of current that can be transferred away. (Assuming the fuse doesn’t blow first).

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13
Q

What is the equation for Power in terms of energy and time?

A

P = E / t

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14
Q

P = E / t rearranged is E = Pt and this expression is used to determine?

A

the energy used by an appliance in a specific time. E.g. A filament lamp (100W) is switched on for 30 minutes. How much energy will it use?

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15
Q

What is the equation for efficiency?

A

Efficiency = useful energy/power output / total energy input (x100)

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16
Q

What does energy equal in terms of current, voltage and time.

A

E = IVt

17
Q

What is alternating current?

A

a current that changes direction repeatedly; every 0.025 / 50 times per second.

18
Q

What is direct current?

A

a current that flows from the positive to the negative terminal.

19
Q

What is amplitude?

A

Maximum displacement of the wave.