b) Draw a free-body diagram depicting equilibrium between the tension on the string
T,weight mgand the Coulomb force F.Using Newton's Second law write a vector
equation depicting equilibrium.
(5 points)
c) Equate vertical and horizontal components of the three forces.
(5 points)
d) Solve the equations for the force in terms of l, m and g.
(2 points)
e) From the force calculate the unknown charge in terms of l, m and g. Let a=
0.2m,l = l.0m,m = 0.005 kg,k = 9 x 109 ,g = 9.80m/s 2 .
(3 points)
5) Two charges q1 = 2nC and q2 = +0.25nC are located on the x-axis separated by 0.3m.
= A third charge q3 -0.SnC is also placed on the x-axis.
(20 points)
a) Set up the equation for the forces acting on q3 due to q1 and q2 .
(10 points)
= b) Find the locations (two solutions) on the x-axis where the force on q3 0.
(10 points)
6) A solid conductor of radius R carries a current I along its axis.
a) Using Ampere's law calculate the B-field inside the conductor. Show the direction of
the B-field.
(10 points)
b) The B-field outside the conductor. Show the direction of the B-field. (5 POINTS)
c) For values of R = 0.0lm, = I l0A, locate and calculate the maximum B-field. Use
(5 POINTS)
(3)