Ohm’s LawWhen a voltage, V is applied across a conductor, the current, i is found to be proportional to the voltage, V. The proportionality constant is the resistance of the conductor R. It is the ability of the conductor to decrease the current flowing through it. The relationship can be mathematically expressed as:
V = IR
The flow of current in a conductor can be compared to the flow of water in a river of equal width and depth. Rocks present on the riverbed can resist the flow of water in the river. Similarly, for conductors resistance reduces the flow rate of current in a conductor. For many, materials, resistance remains constant over a wide range of voltages. This relationship is known as Ohm’s law. Ohm’s Law is not a law of nature. It is an assertion that the current through a device is always directly proportional to the potential difference applied to the device and only applies to certain Ohmic conductors. The resistance in such cases is independent of the magnitude and polarity of the applied potential difference. Similarly materials, which obey Ohm’s Law, have resistivities that are independent of the magnitude and direction of the electric field applied. Semi conductors are non-ohmic in nature.
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Quiz
Which of the following would not obey Ohm's Law?
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