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AS 91526 · 2023 paper · transformers and inductors

Question 2(a) Achieved

Practises Electromagnetic induction: eddy currents & transformers

Kate’s school has a demonstration transformer. She connects the 12 000-turn primary coil to the mains supply at 240 V RMS. The secondary has 600 turns.

N(p)12 000
V(p)240 V RMS
N(s)600

Calculate the RMS voltage she would measure across the 600-turn secondary coil.

The 2023 paper, page 6 ↗ Marking schedule, page 4 ↗

Work it out

Try it on paper first. Stuck? Take one hint at a time.

  1. 1 How is a transformer’s voltage ratio related to its turns?

    Vs / Vp = Ns / Np.

  2. 2 Is the secondary stepping the voltage up or down?

    Down: 600 turns against the primary’s 12 000, a twentieth as many.

  3. 3 Substitute.

    Vs = 240 × 600 / 12 000 = 12.0 V RMS.
Answer 12.0 V RMS

What the marker wanted

  • Achieved The secondary voltage, 12.0 V.

In our words, from NZQA’s 2023 marking schedule.

How did it go?

Got it moves it further out. Review brings it back tomorrow.