NCERT · Class 10 · Science · ElectricityState Ohm's Law. Write the mathematical expression for it and draw a labelled circuit diagram to verify this law experimentally.

Ohm's Law states that the potential difference ($V$) across the ends of a given metallic wire in an electric circuit is directly proportional to the current ($I$) flowing through it, provided its temperature remains constant. Mathematically, this relationship is expressed as $V \propto I$, which can also be written as $V = I \times R$, where $R$ is a constant called resistance for that given wire at a given temperature. The SI unit of resistance is the ohm ($\Omega$). To verify Ohm's law experimentally, a circuit is set up containing a resistor, an ammeter connected in series, a voltmeter connected in parallel across the resistor, a plug key, and a variable resistance (rheostat) connected to a battery source. By altering the current using the rheostat, corresponding potential difference values are recorded, and a straight-line graph plotted between $V$ and $I$ confirms the law.