Two very long straight parallel wires carry steady currents i and $2 \mathrm{i}$ in opposite directions. The distance between the wires is $\mathrm{d}$. at a certain instant of time, a point charge $\mathrm{q}$ is at a point equidistant from the two wires in the plane of the wires. Its instantaneous velocity $\vec{v}$ is perpendicular to this plane. The magnitude of the force, due to the magnetic field acting on the charge at this instant is: A $\frac{\mu_{n} i q v}{2 \pi d}$ B $\frac{\mu_{n} \text { iqv }}{\pi d}$ C $\frac{3 \mu_{n} \mathrm{iqv}}{2 \pi \mathrm{d}}$ D zero

Home » Two very long straight parallel wires carry steady currents i and in opposite directions. The distance between the wires is . at a certain instant of time, a point charge is at a point equidistant from the two wires in the plane of the wires. Its instantaneous velocity is perpendicular to this plane. The magnitude of the force, due to the magnetic field acting on the charge at this instant is: A B C D zero

Two very long straight parallel wires carry steady currents i and $2 \mathrm{i}$ in opposite directions. The distance between the wires is $\mathrm{d}$ . at a certain instant of time, a point charge $\mathrm{q}$ is at a point equidistant from the two wires in the plane of the wires. Its instantaneous velocity $\vec{v}$ is perpendicular to this plane. The magnitude of the force, due to the magnetic field acting on the charge at this instant is:
A $\frac{\mu_{n} i q v}{2 \pi d}$
B $\frac{\mu_{n} \text { iqv }}{\pi d}$
C $\frac{3 \mu_{n} \mathrm{iqv}}{2 \pi \mathrm{d}}$
D zero

Physics | Previous Year Question Papers

Two very long straight parallel wires carry steady currents i and $2 \mathrm{i}$ in opposite directions. The distance between the wires is $\mathrm{d}$ . at a certain instant of time, a point charge $\mathrm{q}$ is at a point equidistant from the two wires in the plane of the wires. Its instantaneous velocity $\vec{v}$ is perpendicular to this plane. The magnitude of the force, due to the magnetic field acting on the charge at this instant is:
A $\frac{\mu_{n} i q v}{2 \pi d}$
B $\frac{\mu_{n} \text { iqv }}{\pi d}$
C $\frac{3 \mu_{n} \mathrm{iqv}}{2 \pi \mathrm{d}}$
D zero

Correct option is (D) zero
Magnetic field at P is perpendicu;ar to paper inward due to both the wires. Charged particle is also projected in the same direction.
So, force on the charged particle is zero as $\overrightarrow{\mathrm{v}} \| \overrightarrow{\mathrm{B}} ; \quad \overrightarrow{\mathrm{F}}_{\mathrm{m}}=\mathrm{q}(\overrightarrow{\mathrm{v}} \times \overrightarrow{\mathrm{B}})=0$

i

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