A straight conductor carries a current. Assume that all free electrons in the conductor move with the same drift velocity `v`. `A` and `B` are two observers on a striaght line `XY` parallel to the conductor. `A` is stationary `B` moves along `XY` with a velocity `v` in the direction of the free electrons.

Options

A. A and B observe the same magnetic field
B. A observes a magnetic field, B doess not
C. A and B observe magnetic fields of the same magntidue but opposite directions.
D. A and B do not observe any electric field

Answer

A,D

Explanation

A is stationary and observes the current I. Observes the free electrons to be at rest, but the unbalanced the free electrons in the conductor will appear to move in the direction opposite to that of v . Thus, A and B observe the same current and hence the same magnetic field.