What is Electrical Resistance | Definition and Unit

In this Post you will learn about Electrical Resistance and its defination and the unit of Electrical Resistance, symbol. the Electrical Resistance is the main and important concept in electrical feild.

Definition - 

It may be defined as the property of a substance due to which it opposes (or restricts) the flow of electricity (i.e., electrons) through it.

When a voltage is applied across a substance there will be an electric current through it. The applied voltage across the substance is directly proportional to the current through it. The constant of proportionality is resistance. Hence resistance is defined as the ratio of applied voltage to the current through the substance.

Where V is voltage, I is current and R is resistance.

The Unit of Resistance

The practical unit of resistance is ohm.

* A conductor is said to have a resistance of one ohm if it permits one ampere current to flow through it when one volt is impressed across its terminals. For insulators whose resistances are very high, a much bigger unit is used i.e., mega-ohm = 10⁶ ohm (the prefix ‘mega’ or mego meaning a million) or kilo-ohm = 10³ ohm (kilo means thousand). In the case of very small resistances, smaller units like milli-ohm = 10⁻³ ohm or micro-ohm = 10⁻⁶ ohm are used. The symbol for ohm is Ω.