The expected answers were:
(a) Lenz’s law states that the direction of an induced e.m.f. is always such that it tends to set up a current opposing the motion or the change of flux responsible for inducing that e.m.f.
(b)(i) B = 0.8 T, I = 20 A, l = 40 cm = 0.40 m
Force F = BIlsin
F = 0.8 x 20 x 0.4 x sin900
F = 6.4 N
(ii) v = 30 m/s
e.m.f., E = Blvsin
E = 0.8 x 30 x 0.40 x sin900
E = 9.6 V
The question was on Magnetic Field and Electromagnetism. The question was unpopular with the candidates. Many candidates as reported could not state the law, some mixed up the expressions for computing force and induce emf while others did not convert the conductor length to metres before using it. The candidates’ performance was not encouraging.