Disc in a magnetic field

Given an aluminum disc of radius R, thickness d, conductivity , and mass density spins on its axis with initial velocity . It passes through poles of a magnet producing a magnetic field perpindicular to the disc over a small area A. With this initial speed how many revolutions will it make before coming to rest?

Potential at the center of a dielectric sphere

Determine the potential at the center of a dielectric sphere with dielectric constant K, radius R, and an embedded uniform charge density rho.

Parallel plate capacitor

1. Consider a parallel plate capacitor, fixed area A, and fixed separation, d. Find the energy stored, and after insertion of a slab of dielectric, which completely fills the space between the plates for each of the two cases (a) The plates are connected to a battery which maintains constant potential difference (b) The plates have fixed charges +Q and -Q and battery disconnected

Energy stored in capacitor

Consider a parallel plate capacitor with area A and separation d. The plates have fixed charges Q and -Q, and no battery connected. Determine the energy stored before and after the insertion of a dielectric with dielectric constant K that completely fills the space between the plates.

Two identical uniform sheet charges...

(See attached file for full problem description with all symbols) -- Two identical uniform sheet charges with =100nC/m2 are located in free space at z = + and - 2.0 cm . What force per unit area does each sheet exert on the other?