The expected answers were:
(a)
Impedance of an a.c. circuit is the opposition of a circuit element or a
combination of circuit elements to current flow.
(b)(i) Impedance, Z = √R2 + (XL-XC)2
= √32 + (8-4)2
= 5Ω
(ii) V = IZ
Current, I = V = 250 = 50A
Z 5
(iii) Power factor = IR = IR = R
V IZ Z
= 3/5 = 0.6
This question was on alternating current circuit theory. It was popular among the candidates. Part (a) was well-answered.
Most candidates answered part (b) very well too. The processes involved in the calculation were well-understood.