26. Capacitors & Dielectrics

What is the potential across a $47\mathrm{\mu }\mathrm{F}$ capacitor that is storing $16\mathrm{\mu }\mathrm{C}$ of charge?

Two pieces of metal are connected to one another by a plastic rod. A student finds that when one has a charge of 12 nC, and the other has a charge of -12 nC, the potential difference between them is $45\mathrm{V}$. What is the capacitance of the arrangement?

A spherical capacitor contains a charge of 3.30 nC when connected to a potential difference of 220 V. If its plates are separated by vacuum and the inner radius of the outer shell is 4.00 cm, calculate: (a) the capacitance; (b) the radius of the inner sphere; (c) the electric field just outside the surface of the inner sphere.

A capacitor is made from two hollow, coaxial, iron cylinders, one inside the other. The inner cylinder is negatively charged and the outer is positively charged; the magnitude of the charge on each is 10.0 pC. The inner cylinder has radius 0.50 mm, the outer one has radius 5.00 mm, and the length of each cylinder is 18.0 cm. (a) What is the capacitance? (b) What applied potential difference is necessary to produce these charges on the cylinders?