Question

A charged particle is always moving parallel to the direction of magnetic field. The magnetic force acting on the particle will be

• A. opposite to its velocity
• B. zero
• C. perpendicular to its velocity
• D. along its velocity

Hint:

Magnetic force depends on the sine of the angle between velocity and magnetic field. Parallel motion gives zero force.

Answer 1

The Correct Option is B

Step 1: Expression for magnetic force.
Magnetic force on a charged particle is given by \[ \vec{F} = q(\vec{v} \times \vec{B}). \]
Step 2: Direction of velocity and magnetic field.
When the velocity vector \( \vec{v} \) is parallel to the magnetic field \( \vec{B} \), the angle between them is \(0^\circ\).
Step 3: Evaluating the force.
\[ |\vec{F}| = qvB\sin 0^\circ = 0. \]
Step 4: Conclusion.
Hence, the magnetic force acting on the particle is zero.