Question

A collimated beam of protons is travelling with a constant velocity along X-axis. There is a current carrying solenoid whose axis is also X-axis. If the beam now enters the solenoid along its axis, it will ______

Options

• describe a circular path.

• get deflected along Z-axis.

• get deflected along Y-axis.

• continue to travel undeflected.

Answer 1

A collimated beam of protons is travelling with a constant velocity along X-axis There is a current carrying solenoid whose axis is also X-axis. If the beam now enters the solenoid along its axis, it will continue to travel undeflected.

Explanation:

Inside a long solenoid, the magnetic field is directed along the solenoid's axis, i.e., along the X-axis. The magnetic force on a moving charged particle is given by:

`vecF = q(vecv × vecB)`

Since the proton velocity is `vecv` parallel to the magnetic field `vecB`, the angle between them is 0°. Therefore, the cross product `(vecv × vecB)` is zero, so no magnetic force acts on the protons.

Hence, the proton beam continues to travel undeflected along the axis of the solenoid.