physics
posted by james .
A generator uses a coil that has 280 turns and a 0.45T magnetic field. The frequency of this generator is 60.0 Hz, and its emf has an rms value of 120 V. Assuming that each turn of the coil is a square (an approximation), determine the length of the wire from which the coil is made.

Use the induced E.M.F. to get the product N*A, where A is the coil area and N is the number of turns (280).
Erms = N*w*A*B/sqrt2
w = coil angular frequency = 377 rad/s
The 1/sqrt2 factor relates the rms voltage to the amplitude.
B = 0.45T
You already know N so that gives you the value of A. The length of a side of the square loop is sqrtA.
4*N*sqrtA is the length of wire. 
2(pi)(frequency) = w