Question

Two very long, straight, parallel wires carry steady currents $I$ and $-I$ respectively. The distance between the wires is $d$. At a certain instant of time, a point charge $q$ is at a point equidistant from the two wires, in the plane of the wires. Its instantaneous velocity $v$ perpendicular to this plane. The magnitude of the force due to the magnetic field acting on the charge at this instant is

• A. $\frac{{\mu }_{0}Iqv}{2\pi d}$
• B. $\frac{{\mu }_{0}Iqv}{\pi d}$
• C. $\frac{{2\mu }_{0}Iqv}{\pi d}$
• D. $0$

Answer 1

The correct option is D $0$

Net magnetic field due to the wires will be downward as shown in figure.

Since angle v⃗ and $\overrightarrow{B}$ is ${180}^o$.

Therefore, magnetic force, $\overrightarrow{F}=q(\overrightarrow{V}\times \overrightarrow{B})=0$