waecE-LEARNING
Applied Electricity Paper 2 , Nov/Dec. 2014  
Questions:   1 2 3 4 5 6   Main
General Comments
Weakness/Remedies
Strength




























Question 4

  1. 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.


 

_____________________________________________________________________________________________________
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).


 

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