Electric charge inside a cubical volume

In summary, the conversation discusses finding the total electric charge contained inside a cubical volume using Gauss's Law and the Divergence Theorem. It is determined that the units for Q should be in coul and the error was due to a units problem, which is later resolved.
  • #1
FrogPad
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Would someone be so kind to check if I am doing this properly. I'm confused on the units, as it doesn't seem to be coming out properly.

Q) Assuming that the electric field intensity is [itex] \vec E = \hat x 100 x \,\,(V/m) [/itex], find the total electric charge contained inside a cubical volume [itex] 100 \,\, (mm) [/itex] on a side centered symmetrically at the orgin.

My Work)
Recall:

[tex] \oint \vec E \cdot d\vec s = \frac{Q}{\epsilon_0} [/tex] (Gauss's Law)
[tex] \int_V \nabla \cdot \vec A \, dv = \oint_S \vec A \cdot d\vec s [/tex] (Divergence Thm)

Thus,
[tex] \oint_S \vec E \cdot d\vec s = \int_V \nabla \cdot \vec E \, dv = \frac{Q}{\epsilon_0} [/tex]

[tex] \nabla \cdot \vec E = 100 \,\, (V/m) [/tex]
[tex] 100 (V/m) \int_V \, dv = 100\, (V/m)(100\times 10^{-3})^3(m^3) = \frac{1}{10} \,\, (V/m^2) [/tex]

[tex] \frac{1}{10} \,\, (V/m^2) = \frac{Q}{\epsilon_0} [/tex]

Thus,
[tex] Q = \frac{\epsilon_0}{10} \,\, (v/m^2) = 8.854\times 10^{-12} \frac{coul}{m^3} [/tex]

I thought the units for [itex] Q [/itex] should be in coul? Why am I getting coul per unit volume? Am I not doing this right?
 
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  • #2
Hi, it looks like a units problem, the numbers look fine.

[tex] \nabla \cdot \vec E[/tex] is measured in V/m2, not V/m. Then you multiply by m3, and get Vm. The units of [tex]{\epsilon_0}[/tex] are C/Vm, so Vm cancels and you get C.
 
  • #3
Mighty appreciated my man :smile:

thanks
 

FAQ: Electric charge inside a cubical volume

What is electric charge?

Electric charge is a fundamental property of matter that causes it to experience electromagnetic interactions. It can be positive or negative, and is measured in units of coulombs (C).

What is inside a cubical volume?

A cubical volume refers to a three-dimensional space that has six square faces, with all edges and angles equal. Inside this space, there can be any type of matter or substance, including electric charge.

How is electric charge measured inside a cubical volume?

Electric charge is typically measured using an instrument called an electric field meter. This instrument measures the strength and direction of the electric field, which can then be used to calculate the amount of electric charge present inside a cubical volume.

What factors can affect the electric charge inside a cubical volume?

The amount of electric charge inside a cubical volume can be affected by several factors, including the type and amount of matter present, the strength of the electric field, and the distance between charged particles.

How is electric charge distributed inside a cubical volume?

The distribution of electric charge inside a cubical volume depends on the arrangement and movement of charged particles. In a conductor, the charge is evenly distributed throughout the volume, while in an insulator, the charge is more localized.

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