Ohms law.

The basic law of electricity - Ohms law.

Ohms law explains that Voltage or the potential difference across a conductor in a closed circuit is directly proportional to the current passing through the conductor. The law was named after the German Physicist George Simon Ohm.

     

    That is V α I, by introducing the constant of proportionality ‘R the resistance’

     V = I x R where R is the resistance of the conductor.

About George Simon Ohm (1789 – 1854)

He was a German physicist, who discovered the law named after his name and which is a basic law related to electricity. Die galvanische Kette, mathematisch bearbeitet (tr., The Galvanic Circuit Investigated Mathematically) is the book where ohms law was first published.

Georg Simon Ohm received the Royal Society Copley medal in 1841 and he was made a foreign member of the Royal Society in 1842, and became a full member of the Bavarian Academy of Sciences and Humanities in 1845.

He died at the age of 65 (July 6, 1854) and the physical unit of electrical resistance, the Ohm (symbol: Ω), was named in his honor.

Three formulas of Ohms law.

In an electrical circuit the current passing will be directly proportional to the potential difference across the circuit. The pictorial representation of these formulae can be done as follows.

V = I x R.

 I = V/R

R = V/I. 

From these equations we can find the unknown quantity if we know the other two quantity.

Resistance.

It can be defined as the amount of opposition to the flow of current through a conductor. The unit of resistance is ohms denoted by Ω. The value of resistance of a conductor/ wire depends on its length and area of cross-section. That is the resistance is directly proportional to the length of the conductor and inversely proportional to the cross-sectional area of the conductor at a given temperature.

           

            R α l/A               Where, l – Length of the conductor.

            R = ρ x l/A                    A – Cross-sectional area of the conductor.

                                                ρ – Resistivity or specific resistance of the material.

The resistance of a long wire is higher than the shorter wire as the flow of electrons get obstructed by the collision of more and more ions as they pass through. Similarly, the resistance of the thin wire is higher than that of thick wire.

Application of Ohms law in daily life.

1. Controlling the speed of a ceiling fan.

By adjusting the regulator means we actually adjusting the current flow to the fan by varying the resistance of the circuit to the fan and we know that the speed depends on the current to the fan motor.

2. Designing of resistor to a circuit.

The resistors are used in an electronic circuit to control the current to a specific value, the section of the resistor can be done using ohms law.

3. Design of fuses.

The fuses are the protection devices in a circuit which connected series to the device circuit. The current rating of the fuse can be calculated using the Ohms law.

Electric Power and Ohms law.

We know that electric power is the rate at which electrical energy is transferred in a circuit. It can be found by using the formula,

                 P = V x I, applying the ohms law, we will get the following formulas.

                 P = I² x R.

                 P = V²/R.

                 I = P/V.

                 I = √ (P/R).

                 I = V/R.

                V = I x R.

                V = P/I.

                V = √ (P/R).

                R = V/I.

                R = P/I²

                R = P/V².

The pictorial representation of the above formulae can be done, which is known as Ohms wheel.

Understand the basics in a simpler way helps to solve complex problems.

Thank You.