Average Induced EMF in Loop of Wire Rotated in B-Field

[airkapp]

A 7.2 cm diameter loop of wire is initially oriented perpendicular to a 1.3 T magnetic field. It is rotated so that its plane is parallel to the field direction in .20 s. What is the average induced emf in the loop?

A = πr2

A = π*.001 = .004 m

ФB = BA

= (1.3T)(.004m) = 5.2E-3 Wb

ФB / t = 0-5.2E-3 Wb / .20 s

= -2.6E-2 Wb/s

€ = -(1)( -2.6E-2 Wb/s)

= 2.6E-2 V


I think i messed up in my area of my formula. can someone help me out here.

 

[futb0l]

I don't see any trig functions there... because the loop is rotated, there has to be a change in the dot product of the vectors.

Remember that A . B = |A| |B| cos theta

 

[futb0l]

Now that I think about it - can't you just take BA/t and then times it by 1/root(2) to get the root mean square voltage.