Ohm's Law
Virtual Experiment

Ohm's Law states that the electric current flowing through a metallic conductor is directly proportional to the potential difference applied across its ends, provided the physical conditions (temperature, pressure) remain constant.

Where V = Potential difference (Volts), I = Current (Amperes), R = Resistance (Ohms Ω).

Named after German physicist Georg Simon Ohm (1789–1854), who published the relationship in 1827.

In the Ohm's Law experiment, components are connected as follows:

• Ammeter — in series with the resistor
• Voltmeter — in parallel across the resistor
• Battery/Power supply — provides variable EMF
• Rheostat/Variable resistance — controls current

An ideal ammeter has zero resistance; an ideal voltmeter has infinite resistance.

Plot V on the Y-axis and I on the X-axis.

• If the graph is a straight line through the origin → Ohm's Law is verified
• The slope = V/I = R (resistance)
• Steeper slope → higher resistance
• A curved graph → non-ohmic conductor (e.g. diode, bulb filament)

Use the compare option to plot two resistors on the same graph and observe the different slopes.

• Connections should be neat and tight
• Ammeter must be in series only
• Voltmeter must be in parallel only
• Always start from minimum voltage
• Do not exceed the rated current of the ammeter
• The key should be opened when not taking readings
• Take readings quickly to avoid heating of resistor
• At least 5–6 readings should be taken for a reliable graph