Ohm's Law

Ohm's law is one of the most important and most used laws of electricity. Current is directly -proportional to the electromotive force and inversely proportional to the resistance. That is, if the electromotive force applied to a circuit is increased, the current will be increased in the same proportion, and if the resistance of a circuit is increased, then the current will be decreased proportionally. Likewise a decrease in the electromotive force causes a proportional decrease in current, and a decrease in resistance causes a proportional increase in current. The current depends only upon the electromotive force and resistance and in the manner expressed by the above simple law.

George Simon Ohm, after whom the unit of resistance is named, observed and doc­umented important relationships between three fundamental electrical quantities. He verified a relationship that indicated that electrical current in a circuit was directly related to the voltage applied and inversely related to the circuit's resis­tance. Recall that if two items are directly related, as one item increases, the other item also increases, and it increases proportionately to the first item's increase. If one item goes down, the other item goes down, proportionately. Inversely related means that as one item increases the other item decreases, proportionately, and vice versa. Also recall that in defining some of the electrical quantities, the rela­tionships in Ohm's law were implied in the definitions. For example, an ohm is that amount of resistance that limits current to one ampere when one volt is applied.

The Relationship of Current to Voltage with Resistance Constant

These relationships are stated in a formula known as Ohm's law, where:

Current (amperes) = Potential difference (volts) / Resistance (ohms)

Formula:

 I=V/R; (Amperes = Volts / Ohms)

As you can sec from the formula, if V increases and R remains unchanged, then a larger value V divided by the same value R will produce a larger number for I. This means that with a given resistance value, if voltage is increased, then current must increase also, and it will increase in direct proportion to the voltage change.

Questionnaire:

• Explain more about Ohm’s Law.