Question

A metallic circular plate with radius rr is fixed to a tabletop. An identical circular plate supported from above by a cable is fixed in place a distance dd above the first plate. Assume that dd is much smaller than r.r. The two plates are attached by wires to a battery that supplies voltage V.
Required:
a. What is the tension in the cable?
b. The upper plate is slowly raised to a new height 2d. Determine the work done by the cable by integrating ∫d to 2d F(z)dz, where F(z) is the cable tension when the plates are separated by a distance z.
Express your answer in terms of the variables d, r, V, and constants ϵ0,pi.
W=

c. Compute the energy stored in the electric field before the top plate was raised.
d. Compute the energy stored in the electric field after the top plate was raised.
e. Is the work done by the cable equal to the change in the stored electrical energy? If not, why not?

Answer 1

The tension cable is in relation to the amount of pressure placed on the upper plate