The rotating loop in an AC generator is a square 12.0 cm on a side. It is rotated at 70.0 Hz in a uniform field of 0.800 T. Calculate the following quantities as functions of time t, where t is in seconds. I need help with d and e. (a) the flux through the loop
11.52cos(140πt) mT·m2
(b) the emf induced in the loop
5.067sin(140πt) V
(c) the current induced in the loop for a loop resistance of 2.50 Ω
2.03sin(140πt) A
(d) the power delivered to the loop
4.12sin2(140πt) W (wrong)
(e) the torque that must be exerted to rotate the loop
mN·m

Explanation:

d )

power in an electrical loop = volt x current

= 5.067sin(140πt)  x 2.03sin(140πt)

= 10.286 sin²(140πt) .

10.286 ( 1 - cos 280πt ) / 2

= 5.143 ( 1 - cos 280πt )

e )

Torque on a current carrying loop in a magnetic field

= M B sinθ

M is magnetic moment of coil , B is magnetic field , θ is angle between area vector of coil and direction of  B .

Here magnetic moment of coil

= A i where A is area of coil and i is current .

= .12² x 2.03sin(140πt)

= .029 sin(140πt)

B = .8 T

MB = .8 x .029 sin(140πt)

= .0232  sin(140πt) x sin(140πt)

=.0232 sin²(140πt).

. west