A very long straight wire carries a current (I) directed along positive Y-axis. A point charge +Q moves with velocity (v) along X-axis. The direction of force on the charge at point (5, 0, 0) m is

along positive y-axis

The correct answer is Option (2) → along positive y-axis

Given:

Current $I$ along +Y-axis

Charge $+Q$ moving along +X-axis with velocity $\vec{v}$

Position of charge: $(5, 0, 0)$

Magnetic field due to a long straight wire:

The magnetic field $\vec{B}$ forms concentric circles around the wire (right-hand rule).

At point (5, 0, 0) — which lies on +X-axis — the magnetic field $\vec{B}$ is directed along −Z axis.

Force on moving charge:

$\vec{F} = q(\vec{v} \times \vec{B})$

Given:

$\vec{v}$ → +X direction

$\vec{B}$ → −Z direction

Then:

$\vec{v} \times \vec{B} = (+X) \times (−Z) = −(X \times Z)$

But $X \times Z = −Y$, so

$\vec{v} \times \vec{B} = −(−Y) = +Y$

Hence, the direction of force on the charge is along the +Y-axis.