ENERGY IN TRANSFORMERS
4 marks · NormalA transformer is used to provide power to a small electronic device. The input voltage is 230 V and the input current is 0.080 A. The transformer is 100% efficient. The output current is 0.46 A.
Calculate the output voltage.
State the formula used for your calculation.
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) 40 V
(b) VpIp = VsIs or input power = output power
Common mistakes: Dividing voltage by current rather than using power equivalence
Show mark scheme and worked solution
Marking points
M1 (a) · 1 mark · Selects/uses VpIp = VsIs or equivalent for transformer efficiency.
M2 (a) · 1 mark · Correct substitution: (230 V x 0.080 A) = Vs x 0.46 A. (follow-through)
A1 (a) · 1 mark · Accurately obtains Vs = 40 V (±0.5). (follow-through)
B1 (b) · 1 mark · Correctly writes VpIp = VsIs or input power = output power.
Worked solution
Input power = output power (100% efficiency):
Substitute values: