Applied Electricity Paper 2 , Nov/Dec. 2014

Questions:		1	2	3	4	5	6		Main

General Comments
Weakness/Remedies
Strength

Question 4
List: (i) two essential devices of an analogue electrical measuring instrument; (ii) two basic types of scale found in the instrument in 4(a)(i). Fig. 1 is a schematic diagram of a moving-coil instrument. (b) Calculate the value of Rs.
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Observation
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).