Two wires of equal length are bent in the form of two loops. One loop is square shaped, the other is circular. They are suspended in a uniform magnetic field and the same current is passed through them. Which loop will experience the greater torque? Give reasons.
Answer: The circular loop experiences the greater torque.
Solution
Torque on a current loop is , so for the same current and field it is proportional to the enclosed area . For a given perimeter the circle encloses more area than the square, so the circular loop has the larger magnetic moment and therefore the greater torque.
CBSE Class 12 Board · 2005 · All India · Subjective