A capacitor is constructed from two square, metallic plates of sides l and separation d. Charges +Q and -Q are placed on the plates, and the power supply is then removed. A material of dielectric constant is inserted a distance x into the capacitor as shown in Figure P25.49 (page 690). Assume d is much smaller than x.
(a) Find the equivalent capacitance of the device.
(b) Calculate the energy stored in the capacitor.
(c) Find the direction and magnitude of the force exerted by the plates on the dielectric.
(d) Obtain a numerical value for the force when , assuming , the dielectric is glass ( ). and the capacitor was charged before the dielectric was inserted.
Suggestion: The system can be considered as two capacitors connected in parallel.
