Physic please help!
posted by Mary .
I got the correct answer for part (a) but I am unsure of how to tackle part (b). Please help!!!
Interactive LearningWare 22.2 at wiley/college/cutnell reviews the fundamental approach in problems such as this. A constant magnetic field passes through a single rectangular loop whose dimensions are 0.35 m 0.55 m. The magnetic field has a magnitude of 2.1 T and is inclined at an angle of 75° with respect to the normal to the plane of the loop.
(a) If the magnetic field decreases to zero in a time of 0.46 s, what is the magnitude of the average emf induced in the loop?
emf = -N (cos 75) (B-B0/t-t0)
emf = -1 (0.258819)(-2.1T/0.46s)
emf = -1 (0.258819)(-4.565217391)
emf = 1.18156V
(b) If the magnetic field remains constant at its initial value of 2.1 T, what is the magnitude of the rate A / t at which the area should change so that the average emf has the same magnitude as in part (a)?
Your use of significant digits baffles me. There is only two significant digits given in the problem.
This is a non trivial error in physics, especially in labs involving measurement. One cannot create precision with calculators.
http://hyperphysics.phy-astr.gsu.edu/hbase/electric/farlaw.html#c1 is a good summary of Faradays law. You are dealing with changing generating an emf by a changing magnetic flux, magnetic flux is B*area
So Faradays law will be
emf=-N d flux /dt
emf=-N (A*dB/dt + B*dArea/dt)
in part a, dArea/dt was zero. In the second part, dB/dT is zero. So for the same emf in the second part, dArea/dt=dB/dt ,
B=2.1T, and since area is tilted, the effective cross sectional area is
L*W*cosTheta or A cosTheta.
I am not so comfortable with the "correct"response in a) Where is area in the calculations? One cannot ignore the area, as you are dealing with flux. Flux is B*area.
YOu may find some benefit in reviewing Faraday's law.