2020 Phase-2 Electromagnetic InductionMotional EMF - rotating conducting rod/wheel Medium Question 13 of 40 in Electromagnetic Induction

A wheel with 20 metallic spokes each 1 m long is rotated with a speed of 120 rpm in a plane perpendicular to a magnetic field of 0.4 G. The induced emf between the axle and rim of the wheel will be (1 G = $10^{-4}$ T)

A 2.51 V
B $2.51\times10^{-4}$ V
C $2.51\times10^{-5}$ V
D $4.0\times10^{-5}$ V

The answer is B.

Solution

Each spoke acts like a rotating rod; the induced emf across a spoke (and hence between axle and rim, since all spokes are in parallel) is $e=\dfrac{1}{2}B\omega L^2$. $\omega=2\pi\times\dfrac{120}{60}=4\pi\ rad/s$. $e=\dfrac{1}{2}\times0.4\times10^{-4}\times4\pi\times1^2\approx2.51\times10^{-4}$ V.

Concept Motional EMF - rotating conducting rod/wheel

Electromagnetic Induction in past papers

40 questions from this chapter have appeared across 23 exam years.