A student has a parallel-plate capacitor with plate area and plate separation
PHYSICS · Multi-part · CBSE · Physics · Electrostatic Potential and Capacitance · Electrostatic Potential and Capacitance
Problem
A student has a parallel-plate capacitor with plate area A=0.020m2 and plate separation d=1.0mm. The capacitor is connected to a 120 V battery at all times. Initially the space between the plates is air. The student then inserts a plastic sheet of thickness d and dielectric constant κ=4.0 so that it completely fills the gap. Neglect edge effects throughout.
(a) Calculate the energy Uinitial stored in the capacitor before the plastic sheet is inserted.
(b) Determine the energy Ufinal stored after the plastic completely fills the gap.
(c) Using your results, compute the mechanical work Wext done by the student during the insertion. State whether the student had to push on the sheet or restrain it from being pulled in, and explain briefly.