AP Physics C E and M

Question

A magnet is pushed into a solenoid of 20 coils with a cross-sectional area of 4.0x10^-4 m².

As a result, the magnetic field inside the coils changes at a uniform rate from 0.0500 T to 0.180 T in a time interval of 1.90 s.

1. What is the magnitude of the emf in [mV] generated in the solenoid?
2. If a 5 ohm resistor is connected to the solenoid, what is the magnitude of the current flowing through it in [mA]?

Answer 1

emf = Ndφ/dt ... φ=BA thus emf = NAdB/dt = 20*4E-4)(.18-.05)/1.9=5.47E-4

I = 5.47E-4/5 = 1.09E-4 amp