What produces magnetic fields?

moving charges themselves

mew naught

Permeability of free space

Solenoid

A tightly wound helical coil of wire. When current is passed through, the magnetic field is uniform inside the helix (an electromagnet).

Solenoid Rule

Curl right hand fingers in the direction of the current. Thumb points to north pole.

N

of turns

A current loop is

a magnetic dipole (like a bar magnet).

r hat

unit vector from ds to point P

Curl fingers in direction of B. thumb points to…

velocity vector/current vector

Units of B

Gauss

1 gauss =

10^4 T

Ideal Solenoid

External field is 0, internal field is uniform

Ideal solenoid is a great approximation when…

Solenoid’s length is much greater than its diameter.

RHR for solenoids

Curl fingers along current, thumb = B

Magnetic flux is always 0 for what? Why?

for closed surfaces. B field lines always form closed loops. Magnetic monopole does not exist.

Current

Flow of positive charge

Atomic Magnet

Magnetic moment due to electron’s orbital motion