Notes Flashcards
Similar Triangles?
Will always have the same angles but may have different lengths
Scalar has?
magnitude only
Vector has?
both magnitude and direction
Why do we use AC over DC for most of the electrical power?
It can be transformed, stepped up or down
Faradays Law of electromagnetic induction?
Magnitude or voltage induced in a turn of wire is proportional to the rate of change of flux passing through the turn
Eg represents?
Voltage generated in volts
B (beta) represents?
flux density of the field in tesla
I represents?
Active length
Easiest and most common way to control generated voltage?
field rheostat in series
Thumb represents?
Motion of conductor
Pointer (second finger) represents?
direction of field (flux)
Middle finger represents?
Direction of induced electron flow
Source power is always ?
Positive to negative
What is the “prime mover”?
Machine that supplies the mechanical energy to the alternator
Name types of ways an alternator can be started?
Steam turbines, water turbines, windmills, combustion engines
What parts of the alternator has voltage induced in it?
Armature
Sine wave with 2 poles will produce _____ degrees electrical and _______ degrees mechanical?
360
360
Sine wave with 4 poles will produce _______ degrees electrical and _________ mechanical?
720 electrical and 360 mechanical
Alternating current?
changes in both magnitude and direction
Cycle?
Distance from point on a waveform to where it begins repeating
Alternation?
One cycle of a sin wave contains to alternations. (.5 of the sine wave)
Period?
time it takes to complete one cycle
Frequency?
Number of complete cycles that occur in one second
formula for frequency?
f= I/p
amplitude?
max height of the waveform above or below zero axis (PEAK)
Peak value?
maximum positive or negative value of the waveform
Peak to Peak value?
difference between positive or negative value of the waveform
Instantaneous value?
Constantly changing
Instantaneous values formula?
E= Epeak x Sin ō(theta)
Average value of sin wave is ____?
Zero
Average value of one alternation of a sins wave is?
0.637 or 63.7% of peak value
effective value is?
.707 of peak
Faradays Law?
Eg = B x I x v
left hand rule for circles with arrows
arrows on top going right?
arrows on top going left?
right on top is a dot
left on top is an x
How is flux density controlled?
magnitude of current
what do brushes have?
limits on both current and voltage
effective value of a sin wave is ?
.707 of the peak value (rms)
In AC there are other properties that oppose the flow of current, they are?
P - pure ohmic resistance S - skin effect H - hysteresis loss R - radiation loss E - eddy currents loss D - dielectric loss
Frequency formula?
F = 1/P
or
P = 1/F
Frequency/rotation formula?
F = PxN/120
Faradays formula?
Eg = B x I x v
Instantaneous formula?
E inst = Epeak x Sine angle
