College Physics III – Thermodynamics, Electricity, and Magnetism

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Surface charge density

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College Physics III – Thermodynamics, Electricity, and Magnetism

Definition

Surface charge density, denoted as $\sigma$, is the amount of electric charge per unit area on a surface. It is measured in coulombs per square meter ($C/m^2$).

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5 Must Know Facts For Your Next Test

  1. Surface charge density is given by $\sigma = \frac{Q}{A}$, where $Q$ is the total charge and $A$ is the area.
  2. It can be positive or negative depending on the nature of the charges on the surface.
  3. The electric field just outside a charged conductor is directly proportional to the surface charge density and can be calculated using $E = \frac{\sigma}{\epsilon_0}$.
  4. $\epsilon_0$ (the permittivity of free space) has a value of approximately $8.85 \times 10^{-12} C^2/(N \cdot m^2)$.
  5. Surface charge density plays a crucial role in calculating electric fields for various charge distributions.

Review Questions

  • How do you calculate surface charge density?
  • What is the relationship between surface charge density and electric field just outside a conductor?
  • Why is it important to know if surface charge density is positive or negative?
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