A loop of radius r = 3 cm is placed parallel to the xy-plane in a uniform magnetic field = (0.75 T) . The resistance of the loop is R = 18 Ω. Starting at t = 0, the magnitude of the field decreases uniformly to B = 0 in 0.15 seconds. What is the magnitude of the electric current produced in the loop during that time?

i = 0.00077A

Explanation:

Given:

loop radius, r = 3.0 cm = 0.03 m

Area, A = π x r² = π x 0.03² = 0.0028 m²

Magnetic Field, B = 0.75 T

Loop resistance, R = 18 Ω

time, t = 0.15 seconds

Now,

the induced emf is given as:

EMF = - BA/t 1

Likewise,

EMF = iR2

Equate 1 and 2

iR = - BA/t

i = - BA/tR

i = 0.75×0.0028/0.15×18

i = 0.0021/2.7

i = 0.00077A

answer would be letter choice (a),   a ball resting on a shelf. would be another example of potential energy   >   stored energy > not moving.

a ball spinning on a finger   >   kinetic energy > moving energy

a ball rolling on the ground   >   kinetic energy   > moving energy

a   ball flying through the air   > kinetic energy   >   moving energy

hope that                                         : )