Current electr motive forc and resistanc
In this chapter we shall deal with the principles and definitions underlying the measurement of current electricity.
A simple electric circuit may consist of a cell connected by copper wires to one or more resistors or other components to be described later. The cell provides an electromotive force which sets up potential differences across the various circuit components and drives the current through them. These components themselves offer varying degrees of resistance to the flow of the current. Thus, in any electric circuit there are three things which have to be measured:
(1) current, measured in amperes (A);
(2) electromotive force and potential difference, both measured in volts (V);
(3) resistance, measured in ohms (Q).