A condenser microphone is different from dynamic microphone. The condenser microphone, the diaphragm is assembled close to a rigid backplate. This microphone need a battery that is connected to the rigid backplate and the diaphragm to charge or give an electrical potential between the metals. The response of diaphragm to sound is changed since the diaphragm change. The displacement of the diaphragm determine the amount of the current. The diagram below illustrates how the dynamic transducer works:

Condenser Microphone circuit schematic
This condenser microphone is the best choice to be used in controlled environments because it has good sensitivity, has small size and can response extremely wide frequency. But it can distort and overload easily when it placed too close to a high intensity sound source.