TRANSFORMERS AND NATIONAL GRIDS
4 marks · NormalA simplified diagram representing a section of the National Grid is shown below.
On the diagram, draw and label the sections where the voltage is highest and lowest.
Explain, using the diagram, why a step-down transformer is used before electricity enters a factory.
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.
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(a) Highest voltage: transmission line (B to C), lowest voltage: after step-down (D to E) · must show B-C marked 'Highest voltage', D-E marked 'Lowest voltage'
(b) Step-down transformer reduces voltage so electricity is safe and suitable for factory use.
Must show: Highlight highest voltage (B-C), Highlight lowest voltage (D-E), Labels
Common mistakes: Marking 'highest' at the generator or 'lowest' at the transmission line
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · Correctly places and labels the 'highest voltage' section on B-C.
B2 (a) · 1 mark · Correctly places and labels the 'lowest voltage' section on D-E.
M1 (b) · 1 mark · States step-down transformer is before the user/factory.
A1 (b) · 1 mark · Explains this is to make the voltage safe/useable or at the required level.
Worked solution
a) The highest voltage is on the transmission line section (B to C). The lowest voltage is after the step-down transformer (D to E).
b) The step-down transformer reduces the voltage to a safe level that can be used in factories. Without this, the high voltage from transmission lines would be dangerous or damage equipment.