Question

Consider a long. straight wire of cross-section area A carrying a current $i$ Let there be . $n$ free electrop volume an observer sitting in the car moving the same direction to the current with a speed $v=\left(\ln Ae\right)$ an separated from the wire by a distance r. The magnetic Geld seen by the observer is

• A. $\frac{{\mu }_{0}i}{2\pi r}$
• B. $zero$
• C. $\frac{{\mu }_{0}i}{\pi r}$
• D. $\frac{2\mu d}{\pi }$

Answer 1

The correct option is A $\frac{{\mu }_{0}i}{2\pi r}$

Magnetic field here will be independent of motion of the observer because the velocity with which the movement of the observer is happening=drift velocity of electrons.

$B=\frac{{\mu }_{o}i}{2\pi r}$