Three charges are located at the vertices of a triangle. Compute the tension in the strings.

Three equal charges, Q coulombs are located at the vertices of a triangle as shown in the figure. The charges are connected together by strings as shown in the figure. If the length of each string is L, determine the tension in the strings.

Electrostatics

A certain charge Q is divided into two parts q and Q-q. How the charges Q and q must be related so that when q and (Q-q) placed at a certain distance apart experience maximum electrostatic repulsion.

Conservation of momentum applied to moving charges.

Two identical particles of mass m carry a charge Q each. Initially one is at rest on a smooth horizontal plane and the other is projected along the plane directly towards the first particle from a large distance, with the speed v. Find the closest distance of approach.

Electrostatic energy stored in the capacitor.

(1) A parallel plate capacitor of plate area 2m2 and palte separation 5mm is charged to 10,000V in vacuum. Compute the capacitance, charge, charge density, field strength in the space between the plates and also the energy stored in the capacitor. (2) The charging battery is removed and the space between the plates is filled with a material of dielectric constant 5. Compute the new capacitance, the potential difference, the field strength and the energy stored. (3) The charging battery remains connected and the space between the plates is filled with a material of dielectric constant 5. Compute the new capacitance, the charge, the field strength and the energy stored.

Radioactivity - Rate of beta decay

A radioactive source in the form of a metal sphere of diameter 10^−3m emits beta particles at a constant rate of 6.25 x 10^10 particles per second. If the source is electrically insulated, how long will it take for its potential to rise by 1 volt, assuming that 80% of emitted beta particles escape from the surface.