USING TRANSFORMERS TO CHANGE VOLTAGES

4 marks · Normal

The primary coil of a transformer is supplied with 230 V and there is a current of 0.1 A in the primary. If the secondary voltage is 23 V, and the transformer is 100% efficient, calculate the secondary current.

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1.0 A (±0.05)

Also accept: Accept answer with correct working.

Common mistakes: Divide instead of multiply when rearranging for current

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Marking points

M1 · 1 mark · Writes input power = output power equation: .

M2 · 1 mark · Substitutes correct values for voltages and primary current.

A1 · 1 mark · Rearranges to find secondary current.

A2 · 1 mark · Evaluates correct value for : 1.0 A (accept follow-through). (follow-through)

Worked solution

For a 100% efficient transformer:

Substitute values: