Question

Choose the correct option concerning magnetic forces and fields?

I. The magnetic field lines due to a current-carrying wire radiate away from the wire.

II. A charged particle can move through a magnetic field without feeling a magnetic force.

III. The kinetic energy of a charged particle can be increased by a magnetic force.

• A. I only
• B. II and III only
• C. I and II only
• D. II only
• E. I and III only

Answer 1

The correct option is D II only

I. The magnetic field lines due to a current-carrying wire do not radiate away from the wire instead of this they curl the wire.

II. A charged particle can move through a magnetic field without feeling a magnetic force , it is possible when it is moving parallel to the magnetic field

$F=qvB\sin \theta$

if $\theta =0$ then $F=0$

III. The kinetic energy of a charged particle can not be increased by a magnetic force because magnetic force does not increase the speed of particle as there is no component of force parallel to velocity so it can only change the direction of charged particle,since kinetic energy depends upon speed so it will not change.