Question

The magnetic field in the center of a horizontal circular loop with a radius of 3 mm is 2.0˛10-5 T and is directed vertically up. What is the magnitude of current in the loop and its direction, when viewed from above? A) 300 mA, counterclockwise B) 300 mA, clockwise C) 95 mA, counterclockwise D) 95 mA, clockwise E) 48 mA, clockwise

Answer 1

Radius r = 3 mm

             = 3 x10 ^-3 m

Magnetic field B = 2 x10 ^-5 T

Magnetic field at the center of the horizontal circular loop B = $\mu _{o}i /2r$

Where $\mu _{o}$ = permeability of free space = 4 $\pi$ x10 ^-7 H/m

From this current i = 2rB / $\mu _{o}$

                           = (2 x3x10 ^-3 x2 x10 ^-5 ) / ( 4 $\pi$ x10 ^-7 )

                           = 0.095 A

                           = 95 mA counterclockwise