Question:medium

A straight conductor carries a current of 5 A. An electron travelling with a speed of $5\times 10^{6}\mathrm{ms}^{-1}$ parallel to the wire at a distance of $0.1\mathrm{m}$ from the conductor, experiences a force of}

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Force on a moving charge due to a current-carrying wire: $F = \frac{\mu_0 I e v}{2\pi r}$.
Updated On: May 3, 2026
  • $8\times 10^{-20}\mathrm{N}$
  • $3.2\times 10^{-19}\mathrm{N}$
  • $8\times 10^{-18}\mathrm{N}$
  • $1.6\times 10^{-19}\mathrm{N}$
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The Correct Option is C

Solution and Explanation

To solve this problem, we need to calculate the magnetic force experienced by an electron traveling parallel to a current-carrying straight conductor. Here's how we can solve it step-by-step:

The magnetic field \(B\) at a distance \(r\) from a long straight conductor carrying current \(I\) is given by the formula:

\(B = \frac{\mu_0 I}{2 \pi r}\)

where \(\mu_0 = 4\pi \times 10^{-7} \, \mathrm{T \cdot m/A}\) is the permeability of free space.

Substitute the given values into the formula:

\(I = 5 \, \mathrm{A}\)\(r = 0.1 \, \mathrm{m}\)

\(B = \frac{4\pi \times 10^{-7} \times 5}{2 \pi \times 0.1} = 10^{-6} \, \mathrm{T}\)

Next, calculate the magnetic force \(F\) experienced by the electron using:

\(F = qvB \sin \theta\)

The electron is moving parallel to the wire, so \(\theta = 90^\circ\) and \(\sin \theta = 1\).

Given the charge of an electron \(q = 1.6 \times 10^{-19} \, \mathrm{C}\) and its speed \(v = 5 \times 10^{6} \, \mathrm{ms^{-1}}\), substitute the values:

\(F = 1.6 \times 10^{-19} \times 5 \times 10^{6} \times 10^{-6}\)

\(F = 8 \times 10^{-18} \, \mathrm{N}\)

Thus, the force experienced by the electron is \(8 \times 10^{-18} \, \mathrm{N}\).

This matches the correct answer from the given options.

Therefore, the correct answer is \(8 \times 10^{-18} \, \mathrm{N}\).

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