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
