Surface charge density

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 ($C/m^2$).

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?

Related terms

Electric Field: A vector quantity that represents the force per unit charge exerted on a test charge at any point in space.

Permittivity of Free Space ($\epsilon_0$): A physical constant that describes how an electric field affects and is affected by a vacuum. Its value is approximately $8.85 \times 10^{-12} C^2/(N \cdot m^2)$.

Linear Charge Density: $\lambda$, which represents charge per unit length, measured in coulombs per meter ($C/m$).