# A rotating coil measuring the magnetic field

by lfused
Tags: coil, field, magnetic, measuring, rotating
 P: 208 The magnetic flux across the coil is $$\Phi = NBA\cos \phi = NBA \cos \omega t\, .$$ that is, varies sinusoidally. Taking the derivative, we find the induced EMF: $$E = -\frac{d\Phi}{dt} = NBA\omega \sin \omega t\, .$$ Ohm's law gives $$I = \frac{E}{R} = \frac{NBA\omega}{R} \sin \omega t\, .$$ The maximum value of current can now be clearly seen. So, you've almost guessed your equation right. Next time you could try using dimensional analysis to see if it's a legal expression or not.