c. Resistance. In all conductors there is some opposition to the movement of
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.
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:
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.
Memory aid for learning Ohm's law.