TRANSFORMERS AND NATIONAL GRIDS
4 marks · NormalThe diagram shows a simplified section of the National Grid.
Explain why a step-up transformer is used before electricity enters the transmission line.
Explain why a step-down transformer is needed before electricity is supplied to consumers.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
Show answer
(a) —
(b) —
Show mark scheme and worked solution
Marking points
M1 (a) · 1 mark · States that increasing voltage reduces current in the transmission line.
A1 (a) · 1 mark · Correctly explains that lower current reduces energy loss as heat during transmission.
M2 (b) · 1 mark · States that voltage is decreased by the step-down transformer before distribution.
A2 (b) · 1 mark · Explains that this is necessary so that electricity is at a safe voltage for use in homes or factories.
Worked solution
(a) A step-up transformer increases the voltage, which reduces the current for a given power. Lower current means less energy is lost as heat in the transmission cables.
(b) A step-down transformer decreases the voltage to a safer level for use by consumers in homes or factories, as high voltages are dangerous for use with appliances.