00:01
So we have some givens.
00:01
We know the formula for the torque on a solenoid is going to be the number of coils times the current, times the cross -sectional area, times the magnitude of the magnetic field, times sine of phi.
00:15
So for part a, we're going to say that tau equals 165 coils on the solenoid times 1 .20 amps times the cross -sectional area of 6 .7.
00:32
Times 10 to the negative 4th meter squared times the magnetic field of 1 .12 teslas times sign of 90 degrees.
00:43
We know that this is going to be equal to 1.
00:46
So we can say that the torque is going to be equal to 0 .150 newton meters.
00:53
And this would be your answer for part a.
00:55
For part b now, the axis of solenoid is oriented parallel to the magnetic field.
01:12
So we can say that here, phi is going to be equal to zero degrees, and tau is going to be equal to the number of coils times the current, times the area, cross -sectional area, times the magnitude of the magnetic field, times sine of phi, phi, however, is zero degrees.
01:35
So this equals zero and this entire thing, zero newt meters...