9. A circular coil of radius 10 cm and with 125 turns is initially oriented perpendicular to a uniform magnetic field of strength 2.50 mT directed out of the page. The wire carries a current of .250 A. a) Sketch the situation. b) Indicate the direction of the magnetic moment of the coil. c) What is the torque on the coil

Explanation:

Given that:

The radius = 10 cm

No of turns = 125

Current in the coil (I) = 0.250 A

Uniform magnetic field B = 2.50 mT = 2.5 × 10⁻³ T

a) The sketch of the situation can be seen below

b)The magnetic moment of the coil is

where the direction of the magnetic moment is the same and equivalent to the direction of the area vector in the diagram. The region vector of the coil is parallel to the magnetic field.

In this manner, the direction of magnetic moment is perpendicular to the current loop by right-hand rule direction; which implies out of the page.

(c)

The torque

where;

between and B = 0

Thus;