What do you mean by capacitance?

21 Points
15 years ago

Capacitance

A capacitor is said to be charged if its plates carry equal and opposite charges +q and – q. Note that q in not the net charge on the capacitor, which is zero. In our discussion of capacitors, we let q represent the absolute value of the charge on either plate; that is q represents a magnitude only, and the sign of the charge on a given plate must be specified. We can “charge” a capacitor by connecting one of its plates to the positive terminal of a battery and the other plate to the negative terminal. The flow of charge in an electrical circuit is analogous to the flow fluid, and the battery serves as a ‘pump’ for electric charge. When we connect a battery to the capacitor, the battery “pumps” electrons from the positive plate of the capacitor to the negative plate. After the battery moves a quantity of charge of magnitude q, the charge on the positive plate is +q and the charge on the negative plate is – q.

An ideal battery maintains a constant potential difference between its terminals. The positive plate and the wire connecting it to the positive terminal of the battery are conductors and so they must be at the same potential V+ as the positive terminal of the battery.