Question

1. Find the electric field (in vacuum) as a function of position z along the axis of a uniformly charged disk of outer radius R with a hole of radius R in its centre. The charge per unit area on the disk is σ. 2, A straight rod, with uniform charge λ per unit length, lies along the z axis from z=11 to z=12-(Thus, the length of the rod is l2-11.) Find the x and y components of the electric field (in vacuum) at a distance x along the x axis 3. An electric dipole of magnitude p 3x10-12 Cm points along a direction 45° to the positive x and y axes (in the xy plane) in an electric field of 7x103 N/C, which points along the positive x axis. Find the potential energy of the dipole and the torque on the dipole. (Give the magnitude and direction of the torque.). 4. Find the work done in bringing three point charges, qu 3 uC, q2 6 uC, q3 -4 μC, from equally spaced points along a line, where the distance between adjacent points is 8 cm, to the vertices of an equilateral triangle of side length 4 cm. (Note: in their initial position, qi, q2 and qs are in consecutive order along the line.)

Answer 1

The ratio will be a/2 squareroot 2: a/2 squareroot 2: 1 potential energy of dipole is U = P.E = P E cos theta = (3 times 10^-12 cm) (7 times 10^3 N/c) cos 45 degree = 14.84 times 10^-9 J Torque on the dipole T = P times E = PE sin theta = (3 times 10^-12 cm) (7 times 10^3 N/c) sin 45 degree = 14.84 times 10^-9 J