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According to ohm’s law at constant temperature, current flow through the conductor is directly proportional to the potential difference across its ends. Ohm’s law gives relation between current and potential difference.
I α V
V α I
V = IR
Here R is the resistance of conductor. Values of resistance depend on four factors:
- Length of conductor.
- Area of cross section.
- Nature of material.
- Temperature of conductor. NOTE: resistance of all pure metal increases with the rise of temperature and decrease with the lowering of temperature. Define one ohm: one ohm is that value of resistance when potential difference of one volt is applied to its end and current of one ampere flow through it. 1ohm = 1volt / 1amp. S.I. unit of resistance is ohm.