Answer:
U = 4.39 J
Explanation:
Electric field energy stored in the medium or vacuum is given as
[tex]U = \frac{1}{2}\epsilon_0 E^2 V[/tex]
here we know that
[tex]\epsilon_0 = 8.85 \times 10^{-12} [/tex]
E = 81.1 V/m
V = volume
[tex]V = (0.0253)(speed \times time)[/tex]
[tex]V = (0.0253)(3\times 10^8 \times 19.9)[/tex]
[tex]V = 1.51 \times 10^8 m^3[/tex]
now from above formula we have
[tex]U = \frac{1}{2}(8.85 \times 10^{-12})(81.1)^2(1.51 \times 10^8)[/tex]
[tex]U = 4.39 J[/tex]
