Question

An observer $A$ and a charge $Q$ are fixed in a stationary frame $F_1$. An observer $B$ is fixed in a frame $F_2$, which is moving with respect to $F_1$

• A. Both $A$ and $B$ will observe electric fields
• B. Both $A$ and $B$ will observe magnetic fields.
• C. Neither $A$ nor $B$ will observe magnetic fields.
• D. $B$ will observe a magnetic field, but $A$ will not.

Answer 1

Answer: (A), (D)

$B$ will observe a magnetic field, but $A$ will not.

Explanation for correct option

1. An observer $A$ and a charge $Q$ are fixed in a stationary frame $F_1$
2. Hence he will only observe an electric field only
3. Since observer $B$ is fixed in a frame $F_2$, which is moving with respect to $F_1$, will observe electric field due to charge in the frame $F_1$ and magnetic field due to motion of the frame $F_2$
4. So both $A$ and $B$ will be watching electric fields
5. $B$ will look at the magnetic field, but $A$ will not.

Hence option A and D is correct