The Unit of Resistance
The practical unit of resistance is ohm.** A conductor is said to have a resistance of one ohm if it permits one ampere current to flow through it when one volt is impressed across its terminals.
For insulators whose resistances are very high, a much bigger unit is used i.e., mega-ohm = 106 ohm (the prefix ‘mega’ or mego meaning a million) or kilo-ohm = 103 ohm (kilo means thousand). In the case of very small resistances, smaller units like milli-ohm = 10−3 ohm or micro- ohm = 10−6 ohm are used. The symbol for ohm is Ω
Multiples and Sub-multiples of Ohm
| Prefix | Meaning | Abbreviation | Equal to |
| Mega- | One Million | MΩ | 106 Ω |
| Kilo- | One Thousand | kΩ | 103 Ω |
| Centi- | One Hundred | – | – |
| Mili- | One Thousandth | mΩ | 10-3 Ω |
| Micro- | One Millionth | μΩ | 10-6 Ω |
Read article – Laws of resistance
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