Difference between Ohm’s and Joule’s law
Ohm’s law
1) Sir S. Ohm studied the relation between current and potential difference applied across the conductor, which is known as Ohm’s law.
2) Experimentally it is proven that, if physical condition of conductor remains the same, electric current increases linearly with increase in potential difference.
3) Ohm’s law stated that, the electric current flowing through the metallic conductor is directly proportional to the potential difference applied across terminals of conductor provided the physical conditions of conductor remains same.
4) When physical conditions such as length of conductor, area of cross-section, temperature and material of conductor kept constant then,
∴ V α I
∴ V = I R
∴ V/I = R(constant)
5) The proportionality constant represented as ‘R’ is known as the resistance of material of wire.
6) SI unit of resistance is Ohm (Ω) which is named after Sir Ohm
7) The nature of graph obtained in experiment of Ohm’s law verification can be shown as, which is a straight line and passes through origin.
Joule’s law
- Sir Joule studied the relation mechanism of current flow and heat produced due to it, and proposed the law known as Joule’s law.
- Experimentally it is found that the heat generated in the conductor due to flow of electron depends upon current, potential difference, and the time for which the current flows through it.
- Joule’s law stated as, the amount of heat generated in the conductor is directly proportional to square of current (I2) flowing through it, its resistance (R) and the time (t) for which the current flows through the conductor.
- If ‘I’ be the current flowing through conductor of resistance ‘R’ for time ‘t’ ,then the Joule’s law can be written as,
∴ H α I2 , H α R and H α t
∴ H α I2 Rt
∴ H=I2 Rt
5) SI unit of heat energy generated in then used as joule (J)