USING TRANSFORMERS TO CHANGE VOLTAGES

4 marks · Normal

A transformer has 150 turns on its primary coil and 450 turns on its secondary coil. The input alternating voltage is 12 V.

Calculate the output voltage across 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

36 V (±0.5)

Also accept: Correct working shown for transformer equation.

Common mistakes: Incorrect ratio (using secondary/primary instead of primary/secondary); Arithmetic error multiplying/dividing

Show mark scheme and worked solution

Marking points

M1 · 1 mark · Writes correct transformer equation: .

M2 · 1 mark · Substitutes the correct values into the equation.

A1 · 1 mark · Rearranges the equation correctly to make the subject.

A2 · 1 mark · Evaluates final output voltage as 36 V (accept follow-through). (follow-through)

Worked solution

The transformer equation is:

Substitute the numbers:

Rearrange for :

So the output voltage is .