Hi. can you help me to solve the following problems?

thanks for your help.

1.A system of four charges -3q, 2q, -3q and 2q are at rhomb vertex with margin “a” (equals charges at opossed vertex). Find: a) potential energy of system in function of “b” (with b:angle between rhomb adjacent angles) b)Find the angle “b” which the configuration is stable c) to configuration from b) find the net forces that each charge experiment

2.A plates capacitor has two squares plates with area: A= 100 cm2 separated a distance d= 1cm and the space between them is full with two dielectrics with k1=2 and k2=3 as a wedge. If the plates has a voltage 120V. a) What is the capacitanece of system?. b) what is charge density at the plates as function from distance x?. c) what´s polarization charge at the surface between dielectrics?

3. A capacitor is maked with three long coaxial conductor cylinders wit h radios: r1 (internal cylinder), r2 (middle cylinder) and r3 (external cylinder). The conductors are separated with dielectrics with constants k1=3 and k2=8. The conductors internal and external are electric connecting. Find in function from r1 and r2 the value of r3 such that minimize the system capacitance.