Solved: PHYSICS Question for NEET

NEET PHYSICSEasy

Two identical bar magnets are fixed with their centres at a distance $d$ apart. A stationary charge $Q$ is placed at $P$ in between the gap of the two magnets at a distance $D$ from the centre $O$ as shown in the figure. The force on the charge $Q$ is:

zero.

directed along $OP$ .

directed along $PO$ .

directed perpendicular to the plane of the paper.

Step-by-Step Solution

Lorentz Force Law: The magnetic force ( $\mathbf{F}$ ) exerted on a charge $q$ moving with velocity $\mathbf{v}$ in a magnetic field $\mathbf{B}$ is defined by the equation: $\mathbf{F} = q(\mathbf{v} \times \mathbf{B})$ [Source 191, Eq. 4.3]
Condition of the Charge: The problem specifies that the charge $Q$ is stationary. This means its velocity vector $\mathbf{v} = 0$ .
Force Calculation: Substituting $\mathbf{v} = 0$ into the Lorentz force equation: $\mathbf{F} = Q(0 \times \mathbf{B}) = 0$ The cross product of a zero vector with any field vector is zero.
Conclusion: A stationary electric charge does not experience any force due to a magnetic field, regardless of the strength or direction of the field produced by the bar magnets .

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