THE TRANSFORMER
3 marks · EasyA transformer has 120 turns on its primary coil and 480 turns on its secondary coil. The input voltage is 6 V a.c.
Is this transformer a step-up or a step-down transformer? Explain your answer.
Calculate the output voltage from the secondary coil.
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) Step-up transformer, because the secondary coil has more turns than the primary coil.
(b) Output voltage = 24 V
Common mistakes: Confusing primary and secondary coil turns; Incorrect use of transformer formula
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · Correctly identifies as step-up and gives a valid reason (secondary turns > primary turns).
M1 (b) · 1 mark · Correct substitution into the transformer equation (or equivalent values).
A1 (b) · 1 mark · Correct answer: 24 V (accept values in range 23.5–24.5 V to allow rounding).
Worked solution
a) The secondary coil has more turns than the primary coil (480 > 120), so this is a step-up transformer.
Substitute the values: