# EM Wave questions

1. Apr 28, 2010

### stanli121

1. The problem statement, all variables and given/known data

with an average total power Pav = 70, 000 W at a frequency f = 98 MHz. A radio
receiver uses the induced emf in a single circular wire loop of radius r = 5.0 cm to
If the maximum induced emf must exceed 0.0050 V to be detectable, find the maximum
distance d the receiver can be from the transmission tower and detect the wave.
(The distance d is much greater than the wavelength  of the wave.)

2. Relevant equations

S = EB/uo
I = P/4(pi)r^2
I = E(rms)^2/c*uo
E or B are functions given by E(x,t)=Esin(kx-wt) or B(x,t)=Bsin(kx-wt)
c=f(wavelength) and k = 2(pi)/(wavelength)

3. The attempt at a solution

I started with the end and went for V = -dflux/dt. I found the flux of the B field through the loop and then differentiated B(x,t) wrt time. I have an expression for this but I'm not sure what the B coefficient in the B(x,t) equation (max value of B) should be or what to do about the cos(kx - wt) term. Any help on where to go for this problem?