What is Absolute and Relative Permitivity.

Sunil Bhardwaj

Permittivity is the property of a particular medium which affects the magnitude of the force existing between two point charges.

We know that the greater the value of the permittivity of the medium placed between the two charged bodies the lesser the value of force existing between them.

Absolute permittivity ${ \epsilon }_{ 0 }$

Relative permittivity ${ \epsilon }_{ r }$

The absolute permittivity of air or vacuum is minimum and its value is $8.854 \times { 10 }^{ -12 }$ F/m (farad/metre) whereas the value of absolute or (actual) permittivity $ \epsilon $ of all other insulating medium is more than ${ \epsilon }_{ 0 }$.

The ratio of these two permittivities i.e. absolute permittivity ($ \epsilon $) of the insulating medium to the absolute permittivity (${ \epsilon }_{ 0 }$) of the air or vacuum is known as relative permittivity of that medium and is denoted by ${ \epsilon }_{ r }$. i.e. $$\quad { \epsilon }_{ r } = \frac { \epsilon }{ { \epsilon }_{ 0 } } $$

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