Question

Four wires, each of length 2.0 m, are bent into four loops P, Q, R and S and then suspended in a uniform magnetic field. If the same current is passed in each, then the torque will be maximum on the loop

• A. P
• B. Q
• C. R
• D. S

Answer 1

Answer: (D)

S

for a given perimeter , a circle has the largest area So,

$\overrightarrow{\tau }=\overrightarrow{M}\times \overrightarrow{B}$

$\tau =inAB$

So, $\tau \alpha A$

So, area is greater leads to more torque

So, loop $S$ will have highest torque (couple).