c. Resistance. In all conductors there is some opposition to the movement of

electrons.

This property, which depends on temperature and dimensions of the

conductor, is known as resistance. Resistance becomes a very important property of

electrical circuits. Its unit of measure is the ohm.

3.

OHM'S LAW

a. Definition.

Ohm's law, simply expressed, is as follows:

For any dc

circuit or part of a circuit under consideration, the current is equal to the EMF

divided by the resistance. The following equation expresses the relationship:

It is common practice to use the following symbols:

E is voltage

I is current

R is resistance

Using these symbols, Ohm's law may be written:

A simple memory aid for this relationship is shown in figure 2. Simply cover the

symbol of the desired quantity (I, E, or R), and the relationship of the remaining

two quantities will be shown by the circle.

Figure 2.

Memory aid for learning Ohm's law.