Electrical resistance is defined as the force that opposes to the flow of electric current. Resistors are used to limit the flow of electric current in the circuit.
According to Ohm's law, electric resistance is calculated with the formula below:
Resistance = V (Potential Difference) / I (Electric current through the object)
SI unit of electrical resistance is ohm. Other common units are milliohm, microohm and volt/ampere.