Question

A parallel-plate capacitor has capacitance 7.00 μF.

(a) How much energy is stored in the capacitor if it is connected to a 4.00-V battery? μJ

(b) If the battery is disconnected and the distance between the charged plates doubled, what is the energy stored? μJ

(c) The battery is subsequently reattached to the capacitor, but the plate separation remains as in part (b). How much energy is stored? μJ

Answer 1

and

--------------------------------- a ----------------------------------------------

Energy stored in Capacitor is given by

=

-------------------------- b -------------------------------

If the battery is disconnected and the distance between the charged plates doubled.

Since the battery is disconnected the charge on the capacitor will remain constant = Q

and the Capacitance become C'

------------------------------- c -----------------------------------

Voltage across Capacitor = 4 V

and

Capacitance of capacitor is