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CUET · PHYSICS · PYQ PAPER 2025

A long straight wire is carrying a current of 20 A. An electron is moving with a speed of \( 10^7 \text{ m/s} \) parallel to the wire. The force experienced by the electron when it is 2 cm away from the wire is:

  1. A \( 3.2\pi \times 10^{-15} \text{ N} \)
  2. B \( 3.2 \times 10^{-4} \text{ N} \)
  3. C \( \frac{3.2}{\pi} \times 10^{-10} \text{ N} \)
  4. D \( 3.2 \times 10^{-16} \text{ N} \)
Verified Solution

Answer & Solution

Correct Answer

(D) \( 3.2 \times 10^{-16} \text{ N} \)

Step-by-step Solution

Detailed explanation

\( B = \frac{\mu_0 I}{2\pi r} = \frac{4\pi \times 10^{-7} \times 20}{2\pi \times 0.02} = 2 \times 10^{-4} \text{ T} \) \( F = qvB\sin\theta = (1.6 \times 10^{-19}) \times (10^7) \times (2 \times 10^{-4}) \times \sin(90^\circ) \) \( F = 3.2 \times 10^{-16} \text{ N} \)