# Definition:Resistance

## Definition

Resistance is a measure of how difficult it is to pass an electric current through a conductor.

It is defined as the electromotive force needed to push a unit current through that conductor.

It is conventionally denoted $R$.

### Symbol

$R$

The usual symbol used to denote resistance is $R$.

Its $\LaTeX$ code is R .

### Dimension

$\mathsf {M L^2 T^{−3} I^{−2} }$

This derives from its definition as:

$R = \dfrac {\text {EMF} } {\text {current} }$

### Unit

The SI unit of resistance is the ohm $\Omega$: $1 \, \Omega = 1 \, \mathrm V \, \mathrm A^{-1}$

In the CGS unrationalised electromagnetic system, the base unit of resistance is the abohm $\mathrm {ab\Omega}$.

In the CGS unrationalised electrostatic system, the base unit of resistance is the statohm $\mathrm {stat\Omega}$.

### Conversion Factors

 $\ds$ $=$ $\ds 1$ ohm $\ds \text {corresponds to}$  $\ds 10^9$ abohm (or e.m.u. of resistance) $\ds \text {corresponds to (approximately)}$  $\ds \dfrac 1 9 \times 10^{-11}$ statohm (or e.s.u. of resistance)

## Also see

• Results about resistance can be found here.