What are the magnitude and direction of the total magnetic force on the coil for the following situations?

A rectangular coil with resistance R has N turns, each of length  and width w as shown in Figure P31.29. The coil moves into a uniform magnetic field  with constant velocity . What are the magnitude and direction of the total magnetic force on the coil for the following situations? (Use the following as necessary: NBwv, and R.)

(a) The coil enters the magnetic field.
F =
(b) The coil moves within the field.
F =
(c) The coil leaves the field.
F =
asked Feb 28, 2012 in Physics

Part A and C are both:

to the left

Part B is 0, zero magnitude

Steps:

You are to express the force using these variables: NBwv, and R.

Magnetic Force = N*I*L*B  (*where I=current, L=length)

According to Ohm's law,

I = Voltage / Resistance

Voltage =Emf so,

I = Emf / Resistance

Emf = N*B*L*v

And so

I =  N*B*L*v / R

Now just plug I back into original equation for force:

Magnetic Force = N*(N*B*L*v / R)*L*B

(*note i have used L instead of w, so just replace L with w to get the correct answer)

upon simplifying we get:

answered Mar 2, 2012 by ~Expert~ (3,856 points)
edited Mar 8, 2012
can you tell us the steps please?
Steps have been posted