Question

Capacitor c1 and c2 are 4f and 2f respectively are charged as series combination across 100v battery. The two capacitors are disconnected from each other.They are connected +ve plate to +ve plate and -ve plate to -ve plate.calculate the resulting charge on each capacitor

Answer 1

q = c v
same q on each
v1+v2 = 100
q/c1 +q/c2 = 100
q/4 + q/2 = 100
3 q/4 = 100
q =400/3 on each

now same v on each and total charge=800/3 and total c = 6
v = q/c = 800/18 = 44.4 volts