Capacitor problem

A 6 microfarad capacitor is charged to an unknown potential Vo and then connected across an initially uncharged 13 microfarad capacitor. If the final potential difference across the 6 microfarad capacitor is 30 V, determine Vo. Answer in units of V

Parallel plates

When a certain air-filled parallel-plate capacitor is connected across a battery, it acquires a charge (on each plate) of magnitude 178 microcoulombs. While the battery connection is maintained, a dielectric slab is inserted into the space between the capacitor plates and completely fills the region. This results in the accumulation of an additional charge of 337 microcoulombs on each plate. What is the dielectric constant of the slab?

Coaxial cable

Neglect end effects. The region between the conductors is air. Ke =1/4*pi*epsilon= 8.98755e9 N m^2/C^2. A coaxial cable has a charged inner conductor (with charge +4.8 microcoulombs and radius 1.199 mm) and a surrounding oppisitely charged conductor (with charge -4.8 microcoulombs and radius 7.405 mm). a)What is the magnitude of the electric field halfway between the two cylindrical conductors in V/m? b)What is the capacitance of this cable in nF?

Resistance of a stretched wire

A wire with resistance R is lengthened to 2.28 times its original length by pulling it through a small hole. What is the resistance of the wire after it is stretched in units of R.

Magnitude of electric field

Consider two concentric spherical shells, one with radius R, and with the radius 2R. Both have the same charge Q. At a point just inside the outershell, the magnitude of the electric field is A. 2kQ/R B. KQ/R C. KQ/2R D. 2kQ/R^2