The national grid

Question 1

The national grid

Answer 1

Electricity is generated in power stations and transported around the UK via the national grid

Question 2

How is power moved around the national grid

Answer 2

Before electrical power leaves a power station, it is transferred at high voltages using step up transformers to increase to voltage from 25,000V to 275,000 or 400,000V. Before electrical power enters homes and factories, the voltages are decreased using step down transformers to 33,000, 11,000 or 230V depending on where it’s going. As high currents waste more energy than low currents, the electrical power is transported around the grid at high voltages but low current.

Question 3

What is a transformer?

Answer 3

A transformer is a device that can change the voltage of an alternating current(ac). A basic transformer is made from two coils of wire: a primary coil from the ac input and the secondary coil from the ac output. The coils are not connected electrically. They are wound around an iron core. This is easily magnetised and can carry a magnetic field from the primary to secondary coils

Question 4

What is a step-up transformer

Answer 4

They are used to step up or increase voltages. A step-up transformer has more turns of the wire on its secondary coil than on its primary coil. This transformer steps up the voltage by reducing the current

Question 5

What is a step-down transformer

Answer 5

They are used to step down or decrease voltages. A step down transformer has fewer turns of wire on the secondary coil than the primary coil. This transformer decreases the voltage by increasing the current.

Question 6

power formula for transformers

Answer 6

power=potential difference x current
power is measured in watts(W)
Potential difference is measured in volts(V)
current is measured in amps (A)