Q. In the figure shown, a uniform magnetic field 0.5 T is perpendicular to the plane of circuit. The sliding rod of length *l* = 0.25m moves uniformly with constant speed *v* = 4ms^{-1}. If the resistance of the slides is 2Ω, then the current flowing through the sliding rod is

(a) 0.1A

(b) 0.17A

(c) 0.08A

(d) 0.03A

Ans: (a)

Sol: The rod can be replaced by a battery of emf e=Bvl and internal resistance r= 2 Ω .

Since , 12 Ω & 4Ω are in parallel . R ‘ = (12×4)/(12+4) = 3 Ω

Now 3 Ω is in series with 2 Ω , Req = 3 + 2 = 5 Ω

Hence current i = e/ Req = Bvl/5 = 0.5 × 4×0.25/5 = 0.1 A