Ohm's law means that in the same circuit, the current passing through a conductor is directly proportional to the voltage at both ends of the conductor and inversely proportional to the resistance of the conductor. This law was put forward by georg simon ohm, a German physicist, in his paper Determination of the Law of Metal Conductivity published in April 1826. In 1849, Kohlrausch studied ohm's law with a delman electrometer.
The current is measured by an ammeter and the potential difference is measured by a quadrant potentiometer. According to the measurement results, the current intensity of the conductor is proportional to the potential difference. With the development of circuit research, people gradually realize the importance of ohm's law, and ohm's reputation is greatly improved. In order to commemorate ohm's contribution to electromagnetism, the unit of resistance is named ohm in physics, which is represented by the symbol ω.
James maxwell's interpretation of Ohm's Law is that the electromotive force of a conductor in a certain state is directly proportional to the current generated. So the ratio of electromotive force to current, that is, resistance, will not change with current. Here, the electromotive force is the voltage across the conductor. With reference to the context of this reference, the modifier "in a certain state" is interpreted as being in a normal temperature state.
This is because the resistivity of a substance usually depends on temperature. According to Joule's law, the Joule heat of a conductor is related to the current. When current is conducted to a conductor, the temperature of the conductor will change. The dependence of resistance on temperature makes the resistance depend on current in typical experiments, so it is not easy to directly test this form of ohm's law.
The first stage of ohm experiment is to explore the relationship between the electromagnetic force attenuation caused by current and the length of wire. The results were published in his first scientific paper 1825 in May. In this experiment, he met with the difficulty of measuring the current intensity. Inspired by the galvanometer invented by German scientist Schveger, he combined the current magnetic effect discovered by Oster with Coulomb torsion balance method.
A current torsion balance is designed to measure the current intensity. Ohm comes from preliminary experiments, and the electromagnetic force of current is related to the length of conductor. This relationship is not directly related to today's ohm's law expression. Ohm did not relate the potential difference (or electromotive force), current intensity and resistance at that time.