Question

A square loop ABCD, carrying a current i, is placed near and coplanar with a long straight conductor XY carrying current I–

• A. There is no net force on the loop
• B. The loop will be attracted by the conductor only if the current in the loop flows clockwise
• C. The loop will be attracted by the conductor only if the current in the loop flows anticlockwise
• D. The loop will always be attracted by the conductor

Answer 1

Answer: (B)

The loop will be attracted by the conductor only if the current in the loop flows clockwise

Answer 2

i = $\frac { \varepsilon } { \mathrm { R } + \mathrm { r } }$ power delivered to R = P = i²R = $\frac { \varepsilon ^ { 2 } r } { ( \mathrm { R } + \mathrm { r } ) ^ { 2 } }$ ,

= 0

Ž R = r