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 × 10⁻⁴ V (c) 2.51 × 10⁻⁵ V (d) 4.0 × 10⁻⁵ V

Answer: (b). Each spoke: e = 1/2Bω R² = Bπ fR²; the number of spokes does not matter (parallel). f = 120 rpm = 2 rev/s, B = 0.4×10⁻⁴ T e = 0.4×10⁻⁴ × π × 2 × 1² = 2.51×10⁻⁴ V So the answer is (b) 2.51×10⁻⁴ V.

A wheel with 20 metallic spokes each 1 m long is rotated with a speed… | NEET 2020 (Phase 2)

Q26NEET 2020 · PHASE 2Medium

Rotating Conductors & AC Generator

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

Show answer and solution

Answer: (b)

Each spoke: $e = \frac{1}{2}B\omega R^2 = B\pi fR^2$ ; the number of spokes does not matter (parallel).
$f = 120\text{ rpm} = 2\text{ rev/s}$ , $B = 0.4\times10^{-4}\text{ T}$
$e = 0.4\times10^{-4} \times \pi \times 2 \times 1^2 = 2.51\times10^{-4}\text{ V}$
So the answer is (b) $2.51\times10^{-4}\text{ V}$ .

Report a mistake

Rotating Conductors & AC Generator question from NEET 2020 (Phase 2)

More questions on Rotating Conductors & AC Generator