Problem 91PE

Construct Your Own Problem Consider using the torque on a current-carrying coil in a magnetic field to detect relatively small magnetic fields (less than the field of the Earth, for example). Construct a problem in which you calculate the maximum torque on a currentcarrying loop in a magnetic field. Among the things to be considered are the size of the coil, the number of loops it has, the current you pass through the coil, and the size of the field you wish to detect. Discuss whether the torque produced is large enough to be effectively measured. Your instructor may also wish for you to consider the effects, if any, of the field produced by the coil on the surroundings that could affect detection of the small field.

Solution 91PE

max = (100 ) (50 x 10 -3 A) (7.0 x 10-2 m)(0.05 T)

= 1.225 x 10 -3 Nm

Therefore, the torque produced in the coil is 1.225 x10-3 Nm. Such torques can produce significant deflection in a galvanometer and hence can be effectively measured.