The Unit of Resistance ( in tearms of Electrical )

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. megaohm = ${\mathrm{10}}^6$ ohm (the prefix 'mega' or mego meaning a million) or kilohm = ${\mathrm{10}}^3$ ohm (kilo means thousand). In the case of very small resistances, smaller units like milli-ohm = ${\mathrm{10}}^{-3}$ ohm or microhm = ${\mathrm{10}}^{-6}$ ohm are used. The symbol for ohm is Ω.

Prefix	Meaning	Contraction	Equal
Mega Kilo Centi Mili Micro	One Million One Thousand One Hundredth One Thousandth One Millionth	M Ω k Ω - m Ω μ Ω${\mathrm{10}}^6$	${\mathrm{10}}^6$ ${\mathrm{10}}^3$ - $$${\mathrm{10}}^{-3}$ $$${\mathrm{10}}^{-6}$

Table : Multiples and sub-multiples of Ohm

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