No idea where to start with this
A 10cm-radius, 25-loop circular wire coil with 40 ohms of resistance sits in a 50T magnetic field. Over the next eight seconds, the field strength is reduced by one-fifth.
a) How much voltage is induced in the coil?
b) How much current flows in the coil while the field is being reduced?
c) If the field strength is reduced during a two-second time interval instead, how much current would flow in the coil?

Question

No idea where to start with this
A 10cm-radius, 25-loop circular wire coil with 40 ohms of resistance sits in a 50T magnetic field. Over the next eight seconds, the field strength is reduced by one-fifth. 
a) How much voltage is induced in the coil? 
b) How much current flows in the coil while the field is being reduced? 
c) If the field strength is reduced during a two-second time interval instead, how much current would flow in the coil?

irishboy123 · Answer

Faraday's law for induction

$$V = - N \frac{d (BA)}{dt}$$
for (i)  N = 25, calc A(rea) from radius, 

A is fixed, so d(BA)/dt = A dB/dt (and a 1/5 reduction over 8 seconds gives dB = -1/5 * 50T, dt = 8).

anonymous · Answer

Must we assume plane of coil is perpendicular to  magnetic field vector?

irishboy123 · Answer

yes, good point

flux ø = BA if perp and the law really relates dø/dt to emf.  ø = 0 if parallel.....