Basic Electricity Flashcards
Name two examples of insulators
Mica, glass, wood, rubber
Name two examples of good conductors
copper, silver, gold
Name an example of a semi-conductor
silicon, germamnium
A good conductor has 1-__ valence electrons
1-2
A good insulator has __ valence electrons
8
A semi-conductor has __ valence electrons
4
one coulomb is 6.25x10 to the power of 18 electrons
yes
Ampere is described as one _______ per second
coulomb
poles are where the magnetic lines of force enter and leave the _______
magnet
The North Pole always points to the ______ pole of the magnetic
south
magnetic lines of force always complete ______
loops
A ferromagnetic material is any material that behaves like _____ in a magnetic field
iron
Flux density - stronger magnetic force means more lines of _____ per area
force
Magnetic screen is where magnetic lines of force pass through _______
anything
Residual magnetism Is the ability of a material to hold a magnetic _____
field
Factors that affect strength of an electromagnet
- number of ____
2, spacing between ____ - type of ______ used
- amount of _____ flow
- number of turns
- spacing between turns
- type of material used
- amount of current flow
A screen uses soft iron to shield a device, providing an alternate path for the magnetic ____
field
Reluctance is the property that opposes the setting up of ____ lines
flux
Name three methods of demagnetizing?
electrical current
heat
vibration
three precautions to avoid damaging magnets
- do not heat
- do not expose to AC
- do not expose to vibration
- don’t store magnet near another magnet
What is a keeper?
A soft iron piece placed across poles to provide easy path for flux
Low voltage?
31v-750v
High voltage?
751v or more
Extra low voltage?
30v or less
Name two advantages of AC?
- AC can be stepped up or down
2. alternators can be manufactured with much higher voltage and power ratings
What is an alternation?
one full wave form
Frequency is the number of times per second a _______ repeats itself
waveform
Peak value is the maximum value or current or voltage in an AC ______
waveform
Average value is the average value based on ___________ values
instantaneous
“RMS” means
root means square
“In phase” is when the voltage wave and current wave reach peak values, and 0 values at ______ point in time
same
“Out of Phase” is when voltage and current wave reach peak values, and 0 values at ______ points in time
different
Phase angle is the difference in _______ between one phase, or value and another
degrees
Name four factors affecting inductance
- number of turns
- coil diameter
- length of the coil
- core material
A Henry describes the amount of resistance in an _______ load
inductive
Farad is the basic unit of ________ where one coulomb of charge for 1 second yields a potential difference of 1 volt
capacitance
capacitors can _____ voltage to increase motor efficiency
slow
“ICE’ means current in a capacitive circuit slows ______
voltage
In a resistive circuit voltage and current are in _____
phase
In an inductive circuit the current lags voltage by ____ degrees
90
In a capacity circuit the current leads voltage by ___ degrees
90
Name three reasons for power loss in transformers
- resistance in the windings
- hysteresis
- eddy currents
electrical equipment voltage imbalance must be within __%
2%
electrical equipment current imbalance must be within __%
10%
