A capacitor is made from two 1.1-cm-diameter coins separated by a 0.10-mm-thick piece of paper (K = 3.7). A 12-V battery is connected to the capacitor. How much charge is on each coin?

A parallel-plate capacitor has square plates 12 cm on a side separated by 0.10 mm of plastic with a dielectric constant of K = 3.8. The plates are connected to a battery, causing them to become oppositely charged. Since the oppositely charged plates attract each other, they exert a pressure on the dielectric. If this pressure is 40.0 Pa, what is the battery voltage?

A parallel-plate capacitor with plate area 2.0 cm² and air-gap separation 0.50 mm is connected to a 12-V battery, and fully charged. The battery is then disconnected. The plates are now pulled to a separation of 0.85 mm. What is the charge on the capacitor now?

A student wearing shoes with thin insulating soles is standing on a grounded metal floor when he puts his hand on the metal case of a high voltage supply. The voltage inside, 6.3 mm from his hand, is 25,000 V. The student’s hand and the voltage supply form a capacitor, considering the student as a conductor. Another capacitor is between the floor and the student (his feet). Using reasonable numbers for hand and foot areas, estimate the student’s voltage relative to the floor. Assume vinyl-soled shoes 1 cm thick.

A parallel plate capacitor consists of two plates of area $A$ separated by a distance $d$ and filled with a dielectric of permittivity $\epsilon$. Which of the following gives the correct expression for its capacitance?

Two circular plates of radius 2cm are brought together so their separation is 5mm. What is the capacitance of these plates?

A 3 F capacitor is given a potential difference across its plates of 10 V. What is the charge built up on its plates? If the source of the potential difference across the plates is removed, but the plates maintain their charge, what is the new potential difference across the capacitor if the distance between the plates is doubled?