Applied Electricity Paper 2 , Nov/Dec. 2010  
Questions:   1 2 3 4 5 6   Main
General Comments

Question 5

(a) Define the following in terms of alternating current:
(i) peak value;
(ii) instantaneous value.
(b) A sinusoidal signal generated from an a.c. mains is represented by the expression
v = 5 sin 314t volts.
Calculate its:
(i) amplitude;
(ii) r.m.s. value;
(iii) peak-to-peak.


The expected answers were:
(a)(i) Peak value - This is the highest or maximum value attained by an alternating quantity over half a cycle.
(ii) Instantaneous value - This is the value of an alternating quantity at any instant of time.
(b) Given v = Ssin314t volts
Recall v = vmsinwt volts
(i) Amplitude (vm) = 5 volts
(Ii) r.m.s. value =vm/√2= 0.707 xVm
= (0.707 x 5) = 3.5 volts
(iii) Peak-to-peak value = 2 x Amplitude
= (2 x 5) volts = 10 volts
The question was on Alternating Current Circuit Theory. The question was popular. The performance was average.
Many of the candidates answered the recall question well. However, those who did not understand the p