What produces magnetic fields?
moving charges themselves
Permeability of free space
A tightly wound helical coil of wire. When current is passed through, the magnetic field is uniform inside the helix (an electromagnet).
Curl right hand fingers in the direction of the current. Thumb points to north pole.
A current loop is
a magnetic dipole (like a bar magnet).
unit vector from ds to point P
Curl fingers in direction of B. thumb points to…
velocity vector/current vector
Units of B
1 gauss =
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.
Flow of positive charge
Magnetic moment due to electron’s orbital motion