112 CHAP 1-4 NOTES Flashcards
Inverse square law
Force between two
magnetic fields _______
proportional to product of
their magnitudes and
_________ proportional to
square of distance between
them
directly; inversely
permeability
The ease with which a material can be magnetized
Methods to Induce a Current
1.Move the conductor through stationary
magnetic field
2.Move magnetic lines of force across conductor
- Vary strength of stationary magnetic field
through conductor
Factors that effect the effectiveness of solenoids and electromagnets
diameter of the coil, its length, current passing along the coil.
Electromagnetic Induction Required Components
- Magnetic field
- Conductor
- Relative motion
Mutual Induction
- Two coils
- Varying current supplied to
primary coil - Induces current in secondary
coil - Two coils are electrically
insulated from each other
Generators
Convert mechanical to
electrical energy
Slip Rings and Brushes function
- Permits the circuit to remain stationary while the armature rotates
without breaking the electrical contact. - Allows electrons to flow without interruption
American and Canadian generators operate at ____ Hz.
60
Sine wave
One complete turn
of the generator
armature represents
one cycle.
A direct-current generator is made by exchanging the
slip rings for a _________ ,
commutator ring
Motors
Convert electrical to mechanical energy
voltage and number of turns are _____ proportional,
directly
voltage and amperage are ______ proportional.
inversely
the number of turns and amperage are _____ proportional.
inversely
step-up transformer _______ voltage from primary to secondary while _______ amperage
Increase
Decreasing
a step-down transformer _______ voltage from primary to secondary while _______ amperage
Decrease
Increasing
rectification
The process by which alternating current is changed to pulsating direct current
Ferromagnetic
(Magnetic Classification
of Materials)
-Iron, cobalt and nickel
-Highly permeable and greatly susceptible
Paramagnetic (Magnetic Classification
of Materials)
- Platinum and aluminum
- Low permeability and weak attraction
Diamagnetic (Magnetic Classification
of Materials)
Beryllium, bismuth, and lead
* Weakly repelled by all magnetic fields
Nonmagnetic (Magnetic Classification
of Materials)
Wood, glass, rubber and plastic
* Not affected by magnetic fields
Permeability
The ability of a material to become
magnetized
Dc motor uses
Commutator rings
the unit of resistance
Ohms
Resistance Dependent upon four things:
- Material’s conductivity
- Length
- Diameter
- Temperature
