Question

A triangular loop of side l carries a current I. It is placed in a magnetic field B such that the plane of the loop is in the direction of B. The torque on the loop is

• A. Zero
• B. IBl
• C. $\frac { \sqrt { 3 } } { 2 } I l ^ { 2 } B ^ { 2 }$
• D. $\frac { \sqrt { 3 } } { 4 } I B l ^ { 2 }$

Answer 1

Answer: (D)

$\frac { \sqrt { 3 } } { 4 } I B l ^ { 2 }$

Answer 2

Since θ = 90°

Hence $\tau = N I A B = 1 \times I \times \left( \frac { \sqrt { 3 } } { 4 } l ^ { 2 } \right) B$

$= \frac { \sqrt { 3 } } { 4 } l ^ { 2 } B$