a capacitor (A1B1) of capacitance C1 = 2 microfarad is charged under a voltage U1 = 20 V and then isolated.
a) Calculate, the voltage U A1B1 between its plates, its charge Q1 and its energy W1.
b) the plates A1 and B1 are connected to those A2 and B2 , of an uncharged capacitor of capacitance C2 = 4C1. At electric equilibrium, the respective charges of the capacitors become Q'1 and Q'2.
- establish a relation between Q1, Q'1, and Q'2
- compare the final energy of the system to the initial energy of the capacitor (A1B1). Deduce.