The electric field at 4 cm from the center of a long copper rod of radius 2 cm has a magnitude of 4 N/C and is directed outward from the axis of the rod. (a) How much charge per unit length (in C/m) exists on the copper rod?
(b) What would be the electric flux (in N · m^2/C) through a cube of side 3 cm situated such that the rod passes through opposite sides of the cube perpendicularly?

Respuesta :

  • The charge per unit length (in C/m) exists on the copper rod is [tex]1.78\times10^{-11}\rm C/m[/tex]
  • The electric flux through a cube of side 3 cm situated such that the rod passes through opposite sides of the cube perpendicularly is [tex]1.48\times10^{-3}\rm N-m^2/C[/tex].

What is electric flux?

The number of electric lines or force that intersects a given area is called the electric flux.

Given information-

Radius of copper rod is 2 cm.

The electric field strength on the copper rod is 4 N/C.

The electric field at 4 cm from the center of a long copper rod.

  • (a) The charge per unit length (in C/m) exists on the copper rod.

The electric charge can be given as,

[tex]q=\dfrac{4Er^2}{k}[/tex]

Put the values,

[tex]q=\dfrac{4\times4\times(0.02)^2}{8.988\times10^9}\\q=7.12\times10^{-13}[/tex]

The charge per unit length is,

[tex]\lambda=\dfrac{q}{l} \\\lambda=\dfrac{7.12\times10^{-13}}{0.04} \\\lambda=1.78\times10^{-11}[/tex]

Thus, The charge per unit length (in C/m) exists on the copper rod is [tex]1.78\times10^{-11}\rm C/m[/tex]

  • (b) The electric flux through a cube of side 3 cm situated such that the rod passes through opposite sides of the cube perpendicularly.

By the Gauss's law the formula for the electric flux ,

[tex]\phi_e=\dfrac{q}{6a^2\times\varepsilon_0}\\[/tex]

Put the values,

[tex]\phi_e=\dfrac{7.12\times10^{-13}}{6\times3^2\times8.85\times10^{-12}}\\\phi_e=1.48\times10^{-3}[/tex]

Hence the The electric flux through a cube of side 3 cm situated such that the rod passes through opposite sides of the cube perpendicularly is [tex]1.48\times10^{-3}\rm N-m^2/C[/tex].

Hence,

  • The charge per unit length (in C/m) exists on the copper rod is [tex]1.78\times10^{-11}\rm C/m[/tex]
  • The electric flux through a cube of side 3 cm situated such that the rod passes through opposite sides of the cube perpendicularly is [tex]1.48\times10^{-3}\rm N-m^2/C[/tex].

Learn more about the electric flux here;

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