MHT CET · Physics · Magnetic Effects of Current

In hydrogen atom, an electron of charge a revolves in a orbit radius r with speed v. Then, magnetic moment associated with electron is

A $\frac{e v r}{2}$
B $2 e v r$
C $e v r$
D $\frac{e v r}{3}$

Verified Solution

Answer & Solution

Correct Answer

(A) $\frac{e v r}{2}$

Step-by-step Solution

Detailed explanation

Magnetic moment of revolving electron,

μ_{e} = i \times A

where,

i

= current and A = area,

μ_{e} = \frac{e}{T} \times π r^{2}

(As current,

i = \frac{c u r r e n t}{t i m e} = \frac{e}{t}

)
where, T = time period of revolution and r = radius of orbit.

μ_{e} = \frac{e}{2 π r} \times v \times π r^{2}

(∵ T i m e p e r i o d (T) = \frac{d i s t a n c e}{s p e e d})

where, v = velocity of revolving electron

\Rightarrow μ_{e} = \frac{e v r}{2}

Hence, the magnetic moment of revolving electron is

\frac{e v r}{2}

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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