Two small spheres each carrying a charge $q$ are placed $r$ metre apart. If one of the spheres is taken around the other one in a circular path of radius $r$, the work done will be equal to

A capacitor $C$ is fully charged with voltage $V _{0}$ After disconnecting the voltage source, it is connected in parallel with another uncharged capacitor of capacitance $\frac{ C }{2} .$ The energy loss in the process after the charge is distributed between the two capacitors is$.........$$CV _{0}^{2}$

A $2\,\mu F$ capacitor is charged to $100$ $volt$ and then its plates are connected by a conducting wire. The heat produced is........$J$

A parallel plate capacitor is charged fully by using a battery. Then, without disconnecting the battery, the plates are moved further apart. Then,

The separation between the plates of a isolated charged parallel plate capacitor is increased. Which of the following quantities will change?

A $20\,F$ capacitor is charged to $5\,V$ and isolated. It is then connected in parallel with an uncharged $30\,F$ capacitor. The decrease in the energy of the system will be.......$J$