Electrodynamics 1: Electromagnetism and DC Motors Flashcards
Magnetism
- physical phenomenon
- produced by the motion of electric charge
- which results in attractive and repulsive forces between objects
Law of magnetism
like poles repel, unlike poles attract
direction of magnetic field lines
NORTH TO SOUTH ALWAYS
conventional current
flow of positive charge from the positive terminal through an external circuit to the negative terminal
circle with dOt
OUT from page
circle with cross
IN to page
for coils
RIGHT HAND motor rule
for motors
LEFT HAND motor FBI
F thumb, force
B (index finger) flux (north to south)
I middle finger current
strength of a magnetic field
the force per unit current per unit length
the unit is N/m/A
B = F/I x L
Magnetic flux density (B)
representation of the magnitude and direction of the magnetic field that is often referred to as the magnetic field strength.
a measure of the number of field lines/flux () though an enclosed area (loop) in a magnetic field.
Magnetic flux linkage
the product of the number of turns on the coil and the flux through the coil (NΦ). More coils in the same flux density produces more flux.
Lenz’s Law
The induced current flows in a direction so as to set up a magnetic field to oppose the change in magnetic flux.
Faraday’s Law
The EMF induced is directly proportional to the rate of change of magnetic flux linkage.
AC generators advantage
simpler, lighter, less costly, and more rugged than DC generators.
transformed to many different voltages to supply industrial and residential needs.
transported at a very low current causing energy loss in the form of heat to be minimised.
rectified to DC if needed e.g for industrial electrolysis.
ac generator characteristic
A generator converts kinetic (mechanical) energy into electrical energy.
