Electrical Resistance Formula

Electrical resistance is the measure of opposition that a material offers in the flow of electric current. It is one of the basic concepts in physics and electrical engineering. Understanding the concept of resistance enables a person to design circuits, select materials, and troubleshoot electrical systems.

What is Electrical Resistance?

The definition of the opposition provided by a circuit to electric current flow is defined as resistance; it is measured in terms of ohms. It states that for every degree of increased resistance, reduced flowing of the current would be observed because of its corresponding voltage.

Formula

We calculate the electrical resistance of a conductor if we know its length and cross-sectional area. It is the product of the resistivity of the conductor and the length of the conductor divided by its cross-sectional area. In the mathematical form, it is represented as follows: 

  Where,

• R = the resistance

•   = the resistivity of the conductor

• l = the length of the conductor

• A = the area of the cross-section

Resistance with the Use of Ohm's Law

The electrical resistance of a conductor can be computed with Ohms law if the current and the voltage drop across it is known. The formula that can be used in order to calculate the resistance using Ohm's Law is expressed as follows:

Where,

• R = Resistance of the resistor R in ohms (Ω)

• V = Voltage drop in the resistor in volts

• I = Current flowing through the resistor (A)

Solved Problem

Example:An electric circuit carries a current of 6.00 A flowing through a resistor. The voltage drop between one end of the resistor and the other is 150 V. What is the resistance?

Solution:

Here, we know the current and the voltage drop across the conductor hence we can use the Ohm's law to find the resistance as follows:

The resistance is