Services

The links on this page will take you to information about general policies concerning the course, the hours when Dale Human is available, and the tutoring system set up by the Office of Student Educational Services and run from the Alumni Student Union (AMU). The various homework assignment sheets will eventually be available here.

moving

Experiments show that the magnetic field of of moving charge can be expressed as:

μ_o ≡ 4π × 10^-7 N·s²/C² is called the permeability of free space. The constant ε_o that is used in electric field calculations is called the permittivity of free space. Note that ε_oμ_o = 1/c².

loops

Break the circuit up into loops.
Choose the (arbitrary) direction of current flow around each loop.
Use Kirchhoff's second rule to get an equation for each loop.
Solve the set of simultaneous equations.
There can be as many unknowns as there are equations.

resistance

Resistance is the ratio of the potential across a material to the current through the material.
R = V/I (Ohm's Law)
R is called the resistance of a particular object measured between two points. Resistivity ρ is a characteristic of a material, while resistance R is a characteristic of a specific sample of that material, with size and geometry figured in.

Although R is generally considered a constant for a particular resistor, R generally varies with temperature, with a proportionality constant α dependent on the material:

object.

Although most materials are neutral (positive and negative charges balance out), they can be charged by using a second charged object in one of two ways:

Conduction: physical contact between the material and the charged
object, get material charged with same sign as charge of the
original charged object.

Induction: no physical contact between the material and the charged
object, get material charged oppositely from sign of charge of the
original charged object.

positive

Electric charge [from Greek word for amber - ελεκτρον (electron)]:

There are two kinds (positive and negative) of charge; opposite signed charges attract each other, while charges of the same sign repel each other.

Total charge is constant, so any increase in negative charge is balanced somewhere by a corresponding increase in positive charge.

perpendicular

Equipotential surfaces are surfaces on which the potential is everywhere the same. No work is done in moving a charge over an equipotential surface. The electric field at an equipotential surface must be perpendicular to the surface since otherwise there would be a component of the field and also therefore an electric force parallel to the equipotential surface. Then work would be done in moving charges over the surface and the surface would therefore not be an equipotential surface.