The National Grid
The National Grid is a network of power stations, cables and transformers that distributes energy around the country and into homes and businesses.
It starts at the power station where A.C. electricity is generated. This is sent through a step up transformer, which increases the voltage to 400kV, a seriously high voltage. It is sent through the system of pylons and cables at this high voltage and then is put through a step down transformer. In homes, this changes the voltage to 240V, which is much safer for domestic use.
Throughout the system the power, energy transferred per second is the same. Remember that power = voltage x current. When the electricity passes through the step up transformer, the voltage is increased so the current is decreased. We do this because if too much current flows, the wire could heat up and increase its resistance and we would lose more energy along the way. Running at a lower current increases the efficiency.
We use A.C. electricity for two reasons: it is easier to generate and it suffers less power loss so we don't lose as much energy along the way. If we had D.C. electricity in the mains, we would need to build many more power stations to compensate for the energy loss!
It starts at the power station where A.C. electricity is generated. This is sent through a step up transformer, which increases the voltage to 400kV, a seriously high voltage. It is sent through the system of pylons and cables at this high voltage and then is put through a step down transformer. In homes, this changes the voltage to 240V, which is much safer for domestic use.
Throughout the system the power, energy transferred per second is the same. Remember that power = voltage x current. When the electricity passes through the step up transformer, the voltage is increased so the current is decreased. We do this because if too much current flows, the wire could heat up and increase its resistance and we would lose more energy along the way. Running at a lower current increases the efficiency.
We use A.C. electricity for two reasons: it is easier to generate and it suffers less power loss so we don't lose as much energy along the way. If we had D.C. electricity in the mains, we would need to build many more power stations to compensate for the energy loss!
Still confused? A helpful teacher has made this presentation:
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