Electrostatics

Problem 123: A capacitor has two parallel metal plates measuring 0.45 m square each. The distance between the plates is 1 cm in free air. If a dielectric material whose permittivity is 4 and 5 mm thick is placed in the upper plate, leaving an air gap between the bottom plate and the dielectric, what is the capacitance of the capacitor?

Problem 124: A capacitor is composed of two plates separated by a 3-mm insulation whose dielectric constant is 4. An additional piece of 6-mm insulation is inserted between the plates. What is the dielectric constant of the additional insulation if the capacitance of the capacitor decreases to half as much of its original value?

Problem 132: The equivalent capacitance of two capacitors in series is \(0.03\,\mu F\) and when connected in parallel, \(0.16\,\mu F\). If the capacitor with the smaller capacitance is replaced with a capacitor whose capacitance is double as much what will be the new equivalent series capacitance of the combination.

Problem 135: Three condensers of 6, 10 and 15 \(\mu F\) are connected in series across a 200 V supply. If the condensers are disconnected, how much energy can the charged condensers provide if connected across each other with like polarities together?

Problem 142: Two capacitors of 200 and 800 nF, respectively are connected in parallel. The combination is then connected in series with another two capacitors of C and 600 nF connected in parallel. If the total capacitance of the set-up is 500 nF, determine the capacitance C.

An air capacitor consists of two parallel square plates of 60 cm side. When the two plates are 2 mm apart the capacitor is charged to a voltage of 240 V. Determine the work done in separating the plates from 2 mm to 5 mm.