The National Grid Flashcards

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What is the National Grid?

It is a network of cables and transformers. It moves electricity from power stations to homes and businesses across the UK.

Why is electricity sent at a very high potential difference on the National Grid?

A higher potential difference (voltage) means a lower current for the same power. Lower current wastes less energy as heat in the cables.

What does a step-up transformer do, and where is it used in the National Grid?

It increases the potential difference from the power station. It is used before the long transmission lines.

What does a step-down transformer do, and where is it used?

It decreases the potential difference to a safe level. It is used at substations near homes and shops.

Which equation links power, potential difference, and current in the National Grid?

P = V × I (power equals potential difference times current).

Why does a smaller current mean less energy lost in the transmission cables?

Wires get hot when current flows. A smaller current makes much less heating, so less energy is wasted.

Why does the National Grid use alternating current (a.c.) rather than direct current (d.c.)?

Transformers only work with a.c., so a.c. is used to change the potential difference.

What potential difference is supplied to UK homes after the step-down transformer?

About 230 V a.c.

What path does electricity follow from the power station to your home?

From a power station, to a step-up transformer, along transmission lines, to a substation step-down transformer, then to homes.

What type of energy is mainly lost in National Grid cables, and why?

Thermal energy (heat), because the cables have resistance and heat up when current flows.

What is a typical potential difference on National Grid transmission lines?

Up to about 400 kV (kilovolts).

Revision Notes
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