Assume that a stationary electron is a point of charge.What is the energy density u of its electric field at radial distances (a) r ! 1.00 mm, (b) r ! 1.00 mm, (c) r ! 1.00 nm, and (d) r ! 1.00 pm

Respuesta :

Answer:

See explanation.

Explanation:

The energy density [tex]U_E[/tex] of an electric field [tex]E[/tex] is given by

[tex]U_E = \dfrac{1}{2} \varepsilon_0E^2.[/tex]

The electric field [tex]E[/tex] at a distance [tex]r[/tex] due to the electron is

[tex]E = \dfrac{q_e}{4\pi \varepsilon_0r^2 };[/tex]

therefore,

[tex]U_E = \dfrac{q_e^2}{32\pi^2 \varepsilon_0r^4 }.[/tex]

putting in values for [tex]q_e = 1.6*10^{-19}C[/tex] and [tex]\varepsilon_0 = 8.85*10^{-12}C^2/N\cdot m^2[/tex] we get:

[tex]U_E = \dfrac{9.16*10^{-30}}{r^4}[/tex]

(a).

For [tex]r=1.00mm[/tex]

[tex]U_E = \dfrac{9.16*10^{-30}}{(1*10^{-3})^4}[/tex]

[tex]\boxed{U_E = 9.16^{-18}J/m^3}[/tex]

(b)

For [tex]r=1.00mm[/tex]

[tex]U_E = \dfrac{9.16*10^{-30}}{(1*10^{-3})^4}[/tex]

[tex]\boxed{U_E = 9.16^{-18}J/m^3}[/tex]

(c).

For [tex]r =1.00nm[/tex]

[tex]U_E = \dfrac{9.16*10^{-30}}{(1*10^{-9})^4}[/tex]

[tex]\boxed{U_E = 9.16*10^6J/m^3}[/tex]

(d).

For [tex]r = 1.00pm[/tex]

[tex]U_E = \dfrac{9.16*10^{-30}}{(1*10^{-12})^4}[/tex]

[tex]\boxed{ U_E = 9.16*10^{18}J/m^3}[/tex]