TRANSFORMERS AND NATIONAL GRIDS
4 marks · NormalThe diagram below shows part of a National Grid system used to distribute electricity from a power station to homes.
Explain why step-up transformers are used after the power station before transmission.
Explain why step-down transformers are used near homes before the electricity enters houses.
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(a) Step-up transformers increase the voltage and reduce the current for transmission, which reduces energy loss as heat in the cables.
(b) Step-down transformers decrease the voltage to a safer level for use in homes.
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Marking points
M1 (a) · 1 mark · References increase in voltage and reduction in current for transmission.
A1 (a) · 1 mark · Correctly links reduced current to reduced energy (heat) loss.
M1 (b) · 1 mark · Mentions decrease in voltage before entering homes.
A1 (b) · 1 mark · States that lower voltage is safer for household use.
Worked solution
(a) Step-up transformers are used after the power station to increase the voltage and reduce the current. Lower current reduces energy lost as heat in the transmission lines.
(b) Step-down transformers are used near homes to reduce the voltage to a safe level (around 230 V) suitable for household appliances and safety.