Gauss' Law and Electric Potential - Prof. Timothy H. Farris, Study notes of Physics

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24.2 & .3 Gauss' Law & Applications Karl F. Gauss recognized that the flux through any closed surface is proportional to the charge inside (& nothing else). This result is know as Gauss' law:

Example: Find the electric field at a distance d away from a long line of charge.

24.4 Conductors in Electrostatic Equilibrium

Electrostatic equilibrium no net motion of charge.

Properties:

1. E = 0 everywhere inside a conductor

2. Any excess of charge resides on the surface of a conductor

3. E is perpendicular to the surface at the surface and equal to

4. Charge accumulates at "bends" & "corners" of conductors.

Ch 25 Electric Potential

25.1 Potential Difference & Electric Potential

Much as we defined the electric field as the force per unit charge, we define thepotential difference as the change in potential energy per unit charge:

We choose the reference point (where U & V = 0) to be out at infinity

This is the potential at the point P.

Units: Define the volt(V):

A unit of energy frequently used in atomic & nuclear physics is the electron volt (eV). It's the energy an electron receives when moved through a potential difference of 1 volt.

Now, moving not parallel to the field:

This motivates the idea of an equipotential surface where the

potential at every point is the same. The E is everywhere

perpendicular to an equipotential surface.

HW: Ch 24:

• pp
• Q 2,
• P 9, 10, 15, 29, 35, 39,
• Ch 25 p
• P 1,