Magnetic fields Flashcards
Cutting magnets in half
- poles cannot be isolated; a magnet cannot be broken to get a separate north and south pole. Instead, it creates 2 magnets each with a north and south pole.
Magnetic Domains
- in order for a material with domains to become magnetic, the domains have to be aligned by an external magnetic field
- if enough of a materials domains become aligned, the material forms a magnetic dipole and becomes a permanent magnet
Magnetic field lines
- point from north to south
- a compass would align with these lines
- a horseshoe magnet is just a bent bar magnet. the rules still apply
B-field
B - magnetic field strength [T]
Right hand rule #1
- thumb points in direction of the current
- fingers point in direction of the field lines
Drawing in 3D
Conventions to help us out:
Into the paper: x
out of the paper: O
Looped wire
A wire in a loop has a stronger magnetic field inside the loop than outside
Right hand rule #2
- thumb points in direction of the current
- fingers point in direction of the field lines
- palm points in direction of the force
Designing a motor
when electric current is passed through a magnetic field, you get motion
Motors vs. generators
Electric motors convert electricity to motion.
Electric generators convert motion to electricity.
Ampere
One ampere is defined as the current that would cause a force of 2 x 10-7N per meter between 2 long parallel conductors separated by 1m in a vacuum
Fields
g = F/m [N]/[kg]
E = F/q [N]/[C]
B = F/I [N]/[A] = [T]
Magnetic flux
- depends on how perpendicular the current is in relation to the field direction
Max flux: vertical
Less flux: narrow
No flux: horizontal
Magnetic field strength
B = F/ILsin0
F - magnetic force [N]
I - current [A]
L - length of wire in field
sin0 - angle between field and current
**L=vt
**I = q/t
- the force on the wire is proportional to the charge moving perpendicular to the field
- because of these, the perpendicular component must be used in calculations
