COMEDK · Physics · 21. Magnetic Effects of Current

A magnetic field does not interact with:

A A current carrying straight conductor
B An electric charge at rest.
C A moving electric charge
D A moving permanent magnet

Verified Solution

Answer & Solution

Correct Answer

(B) An electric charge at rest.

Step-by-step Solution

Detailed explanation

The magnetic force \(\vec{F}\) on a charge \(q\) moving with velocity \(\vec{v}\) in a magnetic field \(\vec{B}\) is given by the Lorentz force law: \(\vec{F} = q(\vec{v} \times \vec{B})\). If the electric charge is at rest, its velocity \(\vec{v} = 0\). Substituting…

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.

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