TRANSFORMERS AND NATIONAL GRIDS
4 marks · NormalThe table below shows the number of turns and voltage in different parts of a section of the National Grid:
| Transformer | Primary coil turns | Secondary coil turns | Primary voltage (V) | Secondary voltage (V) |
|---|---|---|---|---|
| Step-up | 500 | 10,000 | 20 | |
| Step-down | 2,000 | 200 | 220 |
(a)[2 marks]
Calculate the output (secondary) voltage of the step-up transformer.
(b)[2 marks]
Calculate the input (primary) voltage of the step-down transformer.
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) 400 V
(b) 2,200 V
Show mark scheme and worked solution
Marking points
M1 (a) · 1 mark · Uses correctly for step-up
A1 (a) · 1 mark · Correct final value: 400 V
M1 (b) · 1 mark · Uses correctly for step-down (rearranges for ) (follow-through)
A1 (b) · 1 mark · Correct final value: 2,200 V
Worked solution
a) For the step-up transformer:
So V.
b) For the step-down transformer:
Rearrange for :