Magnetic Fields

Note that x means away, and dot means towards. represents current.

Right Hand Rule

For conventional flow, the direction of current is or magnetic field can be determined with the right hand rule. The thumb will be in the direction of the current, and other finders the direction of the field.
For electron flow, use left hand.

Magnetic Field

Definition

The magnetic field (or B field) is represented as , and its unit is the tesla (Webers per square meter).

Magnetic Permeability

Definition

Permeability is the measure of magnetization that a material obtains in response to an applied magnetic field.

The magnetic permeability in free space is

Magnetic Field of a Straight Conductor

Well,

this constant is

where is the magnetic permeability in free space, so:

Equation

This equation comes from Ampere's Law.

Example

Consider a straight metal rod with current of 30 amps running down it. Find the B field 20 meters to the right of it.

Lorentz's Force Equation

Equation

Consider a charge moving in a magnetic field . The force on the moving charge is given as:

If we have both electric field and magnetic field, the total force on the charge is given as:

Magnetic Field of a Coil or Solenoid

Right Hand Rule: Finders match the coil current direction, thumb points north.

where N is the number of turns.

Equation

This equation comes from Ampere's Law.