3.20 Transformer Calculation

Question 1

What is the ratio between the potential differences across the primary and secondary coils the same as?

Answer 1

The number of turns in the primary and secondary coils

Question 2

Why is a high voltage used to transmit huge amounts of energy through the national grid? (3)

Answer 2

• The national grid has to transfer loads of energy each second, which means it transmits electricity at a high power (as power is the rate of energy transfer).
• Power = potential difference x current, so to transmit the huge amounts of power needed, you either need a high potential difference or a high current.
• But a high current makes wires heat up - there are more charges in a given time doing work (transferring energy) to travel through the cable. So loads of energy is dissipated to the thermal energy stores of the cables and the surroundings.