Question

A horizontal semi-circular wire of radius $r$ is connected to a battery through two similar springs $X$ and $Y$ to an electric cell, which sends current I through it. A vertically downward uniform magnetic field $B$ is applied on the wire, as shown in the figure. What is the force acting on each spring?

• A. $2 \pi r B I$
• B. $\frac{1}{2} \pi r B I$
• C. $BIr$
• D. $2 B I r$

Answer 1

Answer: (C)

$ F_B=i \times 2 r \times B $
$ 2 F=F_B $
$ F={irB}$