Force and torque on a triangular current loop. A rigid loop in the form of an equilateral triangle of side length a is situated in a uniform steady magnetic field of flux density B. The magnetic field lines are parallel to the plane of the loop and are perpendicular to one of its sides, as shown in Fig. 4.49. If a steady current of intensity I is established in the loop, find (a) the force and (b) the torque on each of the loop sides, as well as (c) the net force and (d) the net torque on the loop.
Figure 4.49 Triangular current loop in a uniform magnetic field; for Problem 4.38.
Draw the triangular current loop in a uniform magnetic field.
Figure 1
(a)
As per Figure 1, write the magnetic force on the loop side 1.
Here,
Magnetic flux density vector is
Length vector is
Current is
Hence, the magnetic force on the loop side 1 is .
As per Figure 1, the magnetic force on the loop side 2 .
Here,
Length vector is .
Hence, the magnetic force on the loop side 2 is .
As per Figure 1, calculate the magnetic force on the loop side 3.
Here,
Length vector is
Hence, the magnetic force on the loop side 3 is .
(b)
As per Figure 1, calculate the torque on the loop side 1.
Here,
Magnetic flux density is
Length is
Current is
Length
Hence, the torque on the loop side 1 is .
From Figure 1, calculate the torque on the loop side 2.
Here,
Magnetic flux density is
Length is
Current is
Length
Hence, the torque on the loop side 2 is .
From Figure 1, calculate the torque on the loop side 3.
Here,
Magnetic flux density is
Length is
Current is
Length
Hence, the torque on the loop side 3 is .
(c)
Calculate the net force on the loop.
Hence, the net force on the loop is .
(d)
Calculate the net torque on the loop.
Hence, the net torque on the loop is .