A flat rectangular loop of wire is placed between the poles of a magnet, as show

Question

A flat rectangular loop of wire is placed between the poles of a magnet, as shown in the figure. It has dimensions w = 0.60 m and L = 1.0 m, and carries a current I = 2.0 A in the direction shown. The magnetic field due to the magnet is uniform and of magnitude 0.80 T. The loop rotates in the magnetic field and at one point the plane of the loop is perpendicular to the field. At that instant, what is the magnitude of the torque acting on the wire due to the magnetic field? Please explain!

A) 0.48 Nm

B) 0.83 Nm

C) 0.00 Nm

D) 0.40 Nm

E) 0.96 Nm

Explanation / Answer

Formula for torque is T = B*i*A*N*cos(alpha)

here T is Torque acting

B is magnetic field = 0.8 T

i is current in the loop = 2A

A is the area of the loop = 0.6*1 = 0.6 m^2

N is the No.of turns = 1

alpha is the angle between plane of the loop and the field

here alpha = 90 degrees

then Torque T = B*i*A*N*cos(90)

since cos(90) = 0

then Torque acting is T = 0 Nm

so the correct option is C) 0.00 Nm

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