A triangular loop of each side of length l is placed in an external magnetic field. The plane of the loop is in the direction of the magnetic fied. Find the torque on the loop.

Triangular loop of side having length=L and magnetic field=B
When current(i) is passed through the loop having area (A), then the magnetic dipole moment is given by,
M=iA where, A is the area of the coil
A=
2
1
​
×base×height=
2
1
​
×l×lsin60=
4
3
​

​
l
2

Therefore magnetic dipole moment is,
M=iA=
4
3
​

​
il
2

The angle between the normal of the plane and the applied magnetic field is 90 degree
Now the torque acting on the loop is,
τ=MBsinθ=
4
3
​

​
il
2
Bsin90=
4
3
​

​
iBl
2