# Ohm’s Law

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Physik
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JoVE Core Physik
Ohm’s Law

### Nächstes Video26.7: Non-ohmic Devices

In 1827, a German physicist, Georg Simon Ohm, demonstrated Ohm's law experimentally.

Ohm's law states that the current passing through a material is directly proportional to the voltage across the device under constant surrounding conditions.

Any material that obeys Ohm's law is known as an ohmic material, whereas if it does not obey Ohm's law, it is known as a nonohmic material.

Consider another experimental setup to demonstrate Ohm's law, consisting of a resistor, power supply, switch, voltmeter, and ammeter. The voltage across the resistor is measured using a voltmeter, while the current in line with the resistor is measured using an ammeter.

When the resistor is connected to the power supply, the current flows in the clockwise direction, and the voltmeter and ammeter show positive readings. Conversely, when the leads of the power supply are switched, the current flows in the counterclockwise direction, resulting in negative readings.

A graph plotted between the voltage and current readings is found to be linear. The slope of the line gives the resistance, confirming the resistor to be an ohmic device.

## Ohm’s Law

Many materials exhibit a simple relationship between the values of current, voltage, and resistance, known as Ohm’s law. The current that flows through most substances is directly proportional to the voltage applied to them. The German physicist Georg Simon Ohm (1787–1854) was the first to demonstrate experimentally that the current in a metal wire is directly proportional to the voltage applied. Any material, component, or device that obeys Ohm’s law, where the current through the device is proportional to the voltage applied, is known as an ohmic material or ohmic component. Any material or component that does not obey Ohm’s law is known as a nonohmic material or nonohmic component. In an article published in 1827, Georg Ohm described an experiment in which he measured the voltage across and current through various simple electrical circuits containing various lengths of wire. The experiment was used to observe the current through a resistor that results from an applied voltage.

Another similar experiment was used to observe the current through a resistor that results from an applied voltage. In this simple circuit, a resistor is connected in series with a battery. The voltage is measured with a voltmeter, which is placed in parallel with the resistor. The current is measured using an ammeter and is placed in series with the resistor. Several measurements of the current were carried out for several different voltages. The current through the resistor and the voltage across the resistor were measured, and a graph was plotted between the voltage and the current, which showed an approximately linear relationship. The slope of the line is the resistance, or the voltage divided by the current. The result became known as Ohm’s law.