The expected answers were:
(a) (i) Any two essential devices
Deflecting (or operating) device
Controlling device
Damping device
(ii) Linear scale
Non-linear scale
(b) V = Iara = IsRs
Is = I – Ia = 40 – 0.030 = 39.97 A
Rs = =
Rs = 15.01 mΩ = 15.01 x 10-3 Ω
The question was on Measuring Instruments. It was very popular with the candidates. It showed that many candidates that attempted this did very well but missed part (a)(i).