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AP EAMCET · PHYSICS · Electromagnetic Induction

If a wheel with 24 metallic spokes each 40 cm long is rotated with a speed of \(180 \mathrm{rev} / \mathrm{min}\) in a plane normal to the horizontal component of earth's magnetic field, the emf induced between the axle and the rim of the wheel is E. If the number of spokes is made 12 and the wheel is rotated with a speed of \(90 \mathrm{rev} / \mathrm{min}\) in the same field, the induced emf is

  1. A E
  2. B 2E
  3. C 4E
  4. D 0.5 E
Verified Solution

Answer & Solution

Correct Answer

(D) 0.5 E

Step-by-step Solution

Detailed explanation

\( \mathcal{E} = \frac{1}{2} B \omega L^2 \) \( \frac{\mathcal{E}_2}{\mathcal{E}_1} = \frac{\omega_2}{\omega_1} \) \( \omega_1 = 180 \text{ rev/min} \) \( \omega_2 = 90 \text{ rev/min} \) \( \frac{\mathcal{E}_2}{E} = \frac{90}{180} = \frac{1}{2} \) \( \mathcal{E}_2 = 0.5 E \)