Investigation: Ohm's law

Aim: to verify that the current through an ohmic conductor is directly proportional to the potential difference across it.

• Apparatus: battery, rheostat, resistor, ammeter (in series), voltmeter (in parallel), connecting wires.
• Method: vary the rheostat, recording matching pairs of V and I readings.
• Plot V (y) against I (x): a straight line through the origin confirms Ohm's law.
• The gradient of that line equals the resistance.

• Ohmic conductor — one whose resistance stays constant at constant temperature.
• Rheostat — a variable resistor used to change the current.