A charge Q is moving dl→ distance in the magnetic field B→. Find the value of work done by B→.

Correct answer: (C) Zero. Since force on a point charge by magnetic field is always perpendicular to v→F→=qv→×B→ ∴ Work by magnetic force on the point charge is zero.

Q63 / 90 · JEE Main 2021 (16 Mar Shift 2) · Physics

A charge $Q$ is moving $d \vec{l}$ distance in the magnetic field $\vec{B}$ . Find the value of work done by $\vec{B}$ .

A
$1$
B
Infinite
Correct answer
C
Zero
D
$- 1$

Solution

Since force on a point charge by magnetic field is always perpendicular to $\vec{v} [\vec{F} = q (\vec{v} \times \vec{B})]$

$∴$ Work by magnetic force on the point charge is zero.

Hence, the correct answer is option: 'C'.

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