49. ssm The rectangular loop in the drawing consists of 75 turns and carries a current of

I = 4.4 A. A 1.8-T magnetic field is directed long the +y axis. The loop is free to rotate about the z axis. (a) Determine the magnitude of the net torque exerted on the loop and (b) state whether the 35° angle will increase or decrease.

 

w1121

Draw figure from top looking view

Torque created by the magnetic field interacting with the magnetic moment of the coil is found from

This figure shows the relation of the vectors

The magnitude of the torque is found from

 

 

is the angle between , and  and in this case

 

 

 

 

 

The torque wants to align the magnetic moment with the external magnetic field.  That would imply increasing the angle.  However, let’s apply right and rule to get direction of torque.  Starting at , and rotating your fingers through the smallest angle to   This implies a torque into the paper or clockwise, which again increases angle!

 

The 35° will increase

 

 

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This page last updated on June 21, 2018