Question

What is the energy stored per unit volume in vacuum, where the intensity of electric field is ${10}^{3}V/m$ ?

• A. $8.85\times {10}^{-6}J/m^3$
• B. $4.425\times {10}^{-8}J/m^3$
• C. $4.425\times {10}^{-6}J/m^3$
• D. $8.85\times {10}^{-5}J/m^3$

Answer 1

The correct option is C $4.425\times {10}^{-6}J/m^3$

Given: $E={10}^{3}V/m$

Energy stored per unit volume in electric field is given by,

$Energy=\frac{1}{2}{ϵ}_{\circ }{E}^2$

For vacuum, ${ϵ}_{\circ }=8.85\times {10}^{-12}$

$Energy=\frac{1}{2}\times 8.85\times {10}^{-12}\times ({10}^3{)}^2=4.425\times {10}^{-6}J/m^3$