Question

A proton moving with a constant velocity passes through a region of space without any change in its velocity. If E and B represent the electric and magnetic fields respectively, this region of space may have

• A. $E=0,B=0$
• B. $E=0,B\ne 0$
• C. $E\ne 0,B=0$
• D. $E\ne 0,B\ne 0$

Answer 1

Answer: (A), (B), (D)

The correct options are
A $E=0,B=0$
B $E=0,B\ne 0$
D $E\ne 0,B\ne 0$

Here,

For no change in velocity,

There should be no any net force on the particle,.

It is possible when both $E$ and $B=0,$

Also,

It is possible when $E=0$ and $B\ne 0$ but parallel to $v$

Also,

It is possible when both $E$ and $B\ne 0$ but both cancel each other.

But for $E\ne 0$ and $B=0$

There will be electric force.

Hence Option $\text{A,B,D}$ is the correct answer