Ohm's Law

George Simon Ohm was a 19th century physicist who discovered the relationships among voltage, current, and resistance. This relationship is known as Ohm's Law.



The beauty of Ohm's Law is that if you know any two of the variables, then you can determine the remaining one.

What is the practical value of Ohm's Law? To answer this question, we will focus on a practical example. For the next few moments consider yourself a flashlight designer.

Your circuit is a simple one, using a battery as the power source and a small lamp as the resistance, or load. Figure 2.11 is a circuit drawing (schematic) to guide you.

Figure 2.11

The current in the circuit must be 3 amps, and the only batteries available have a voltage of 3 volts.

What resistance must be produced by the lamp to make your flashlight operate properly?

The correct answer is 1 Ω. If you made a mistake, you should return to the previous paragraphs and re-read them. It is important that you understand Ohm's Law, since resistors are our major products!

The preceding exercise should have demonstrated that Ohm's Law makes it possible to calculate, and thus design, the performance of a simple circuit which uses a battery as a power source.