A rectangular current carrying 54 turn coil, as shown in the figure, is pivoted
ID: 1514559 • Letter: A
Question
A rectangular current carrying 54 turn coil, as shown in the figure, is pivoted about the z axis. The current in the coil is I = 1.70 A. (a) If the wires in the z = 0 plane make an angle theta = 36 degree with the y axis, what angle does the magnetic moment of the coil make with the unit vector i^? (b) Write an expression for n^in terms of the unit vectors i^and j^, where n^is a unit vector in the direction of the magnetic moment. (c) What is the magnetic moment of the coil? (d) Find the torque on the coil when there is a uniform magnetic field B vector = 1.3 T j^in the region occupied by the coil. (e) Find the potential energy of the coil in this field. (The potential energy is zero when theta = 0.)Explanation / Answer
part a)
theta=36º
part b )
n = nxi + nyj
n = cos36 i - sin36 j
n = 0.809 i - 0.587 j
part c )
mu = NIA*n
mu = 54 * 1.70 * ( 8 *10^-2 x 5 *10^-2) ( 0.809 i - 0.587 j )
mu = (0.2970 m^2) i - (0.2155 m^2) j
part d )
t = mu x B
t = [(0.2970 m^2) i - (0.2155 m^2) j ]x (1.3T)j
t = (0.3861 N-m ) k
part e )
U = -mu . B
U = -[ (0.2970 m^2) i - (0.2155 m^2) j ] . (1.3 T)j
U = 0.280 J