1 induced emf calculations I a solid metal object with dimen

1) induced emf calculations:

I) a solid metal object with dimensions 10cmX2cmX6cm (into the page) is moving with a speed of 4m/s through a region where there is a uniform 0.02T magnetic field as shown
A) what is the magnitude of the induced emf?

B) which side acquires a net positive charge(choose one)? left/ right/ top/ bottom/ front/ back

I) the magnetic flux through a coil with 15 turns is given by the equation
(subscript B)= 3t²+15t+40 where (subscript B) is in Webers and T is in seconds. what is the magnitude of the average induced emf over the time interval from t=0 to 20s?

Solution

1) induced emd = B L v

B = 0.02T, L = 6cm = 0.06 m and v = 4m/s

e = 0.02 x 0.06 x 4 = 4.8 x 10^-3 V Or 4.8 mV

(B) front

(I) induced emf = rate of change of magnetic flux

= d( NBA)/ dt = 15 d(3t^2 + 15t + 40)/dt

= 15 (6t + 15)

at t = 0 , emf = 15 * 15 = 225 V

at t = 20s , emf = 15 (6*20 + 15) = 2025 V

average = (225 + 2025) / (2) = 1125 Votl ........Ans