Question

compare the energy density in dielectric with the energy density in air give an expressions to justify your answer ​

Answer 1

The comparison of the energy density in a dielectric with the energy density in air is as follows.

• The electrostatic energy stored
• U = 1/2 q²C
• U = q² / 2ε₀A × d      …... (1)
• (where C is the capacitance, C = ε₀A/d, q is the charge upon capacitor)
• Now the electric field in the space (between plates of capacitor)
• E = q/ε₀A ...... (2)
• From equation (1) and (2),
• U = 1/2 (q/ε₀A)² × ε₀ × A × d
• ⇒ U = 1/2 ε₀ E² × Volume
• Hence U/Volume = 1/2 ε₀E²    ......(3)
• This expression can be compared with magnetic energy per unit volume which is equal to B²/2μ₀