1) If the battery is connected, is the energy of capacitor-battery system conserved throughout the process of inserting the dielectric? Explain the changes of energy, if any.

2) If the battery is disconnected, does the energy stored in the capacitor remain constant as the dielectric is inserted? Explain the changes of energy, if any.

ANSWER:

1. For first case, when we insert dielectric the capacitance of the capacitor changes by k times the initial capacitance. So, the energy stored will also be increased by k times. Here, k is dielectric constant of dielectric material. So, the energy will not be constant. The energy will be increased in the process of inserting dielectric in the form of increasing capacitance which will result in more charge storage on capacitance.

2. For second case, when the battery is disconnected there will not be any process by which charge will change on capacitor. But, when we insert the dielectric, the capacitance will be increase. So, energy will not be constant and will decrease by k times the initial energy as for constant charge on capacitor energy is inverselu proportional to capacitance of capacitor. Here, k is dielectric constant.