We know what is current and voltage. Is there any relation between these two? Yes. It is given by a law that is as basic as the alphabet is to a language.
This is one of the fundamental laws of electrical engineering. Two very common terms in electricity are current and voltage. Ohm’s law connects both of them.
Note that there are different ways of stating Ohm’s law:
Ohm’s law states that for a condition of temperature being constant …..
* ….. the voltage across a conductor is directly proportional to the current flowing through it.
* ….. the current through a conductor is directly proportional to the voltage across it.
* ….. the ratio of voltage across a conductor to the current flowing through it is constant.
The constant of proportionality (R) is called Resistance. Resistance is the property of a material to oppose the flow of current through it.
Resistance is a very important parameter in electrical and electronic circuits. It is used to limit the amount of current in parts of the circuit. As can be seen from the equations, for a constant voltage, current can be reduced by increasing the value of resistance. In electronic circuits, a device called a Resistor is used. Each resistor has a fixed value of resistance.
Resistance is the property of a material to oppose current through it. Resistor is the device having this property.
Unit of Resistance
The unit of resistance is ohm, Ω, after Georg Simon Ohm (1784-1854), a German physicist who postulated the law relating voltage, current with resistance.
Applications of Ohm’s law
As seen from the above equations, knowing two parameters of an electrical circuit, we can calculate the third parameter. Usually, current can be measured using an ammeter, and voltage can be measured using a voltmeter. Though an instrument called ohmmeter is used, we can calculate easily the resistance of a conductor using Ohm’s law, dividing voltage value by current value.
All materials have some form of resistance. The material that allows more current has very low resistance, and is called a conductor. An insulator is a material that allows very little or no current because it has very high resistance.
The resistance of a conductor depends on the type of material and its dimensions. We shall see how they affect the resistance in another article.
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Very easy to understand article about ohms law
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