Final answer:
Georg Ohm studied the resistance of different materials by creating simple electrical circuits to measure the voltage and current, which led to the discovery of Ohm's law. Ohm's law states that for ohmic materials, the resistance is equal to voltage divided by current (R = V/I), and is constant across various voltages and currents. Ohmic materials include good conductors like copper and aluminum, while non-ohmic materials do not show this constant relationship.
Step-by-step explanation:
Georg Ohm studied the resistance of different materials by conducting experiments to measure the voltage across and the current through various simple electrical circuits. In his landmark 1827 paper, Ohm detailed his methodology wherein he connected different lengths of wire in series with a battery and measured the resulting current with an ammeter and the voltage with a voltmeter, which was connected in parallel with the resistor. This experimental setup allowed Ohm to demonstrate the direct proportionality between voltage and current for what came to be known as ohmic materials, such as copper and aluminum. Ohm's law, the foundational principle discovered through these experiments, states that the resistance (R) of a material is equal to the voltage (V) divided by the current (I), expressed as R = V/I, where the resistance is measured in ohms (Ω). Ohm also noted that the relationship defined by Ohm's law is not universally valid. Only certain materials, known as ohmic materials, exhibit a constant resistance that is independent of the voltage and current. This is contrasted with non-ohmic materials which do not follow this simple linear relationship between current and voltage. To verify whether a material is ohmic, one can construct a resistor from the material and measure the current for different voltages. If a material is ohmic, the material's current is directly proportional to the applied voltage, and the resistance remains constant over a range of voltages and currents.