ELA 125 test 3
Alternating current is defined as current which is periodically changing in ______, while continuously
changing in ______ - correct answer ✔✔Direction and Amplitude
The maximum value of an AC sine wave voltage is called the ____ value - correct answer ✔✔Peak
Unless otherwise specified, any values given for current or voltage in an ac circuit are assumed to be the
_____ or _____ value, which is equal to ______% of the peak value. - correct answer ✔✔Effective, RMS,
70
The number of complete cycles which are developed by alternator in a given unit of time is known as the
alternator's output - correct answer ✔✔Frequency
The amount of time needed to generate one cycle of AC is called the - correct answer ✔✔Period
How does the number of poles on the rotor of an alternator affect the output frequency of the unit -
correct answer ✔✔Directly proportional ( more poles, higher frequency at the same RPM)
How does the RPM of the rotor of an alternator affect the output frequency of the unit? - correct answer
✔✔Directly proportional (Higher RPM, higher frequency with the same number of poles)
What is the instantaneous value of voltage of a 200 volt peak sine wave at 30 degrees - correct answer
✔✔200 x Sin(30)= 100 volts
What is the instantaneous value of voltage of a 200 volt peak sine wave at 90 degrees - correct answer
✔✔200 x Sin(90) = 200 volts
What is resistance - correct answer ✔✔Is the opposition to current flow
, What is inductance - correct answer ✔✔Is the property of an inductor by which a change in current
induces a voltage in both itself and nearby conductors
What units are used to measure inductance - correct answer ✔✔Henries (H or h)
How much inductance does a coil have if it induces 5 volts into itself when current is changing at a rate
of 100 amps per second? - correct answer ✔✔5v/100 amps= 50mH
What does L stand for - correct answer ✔✔Inductance
What does N stand for - correct answer ✔✔Number of turns
What does A stand for - correct answer ✔✔core area
What does U stand for - correct answer ✔✔Core Permeability
What does I stand for - correct answer ✔✔Coil Length
If we were to increase the number of turns of wire on a 10 microhenry coil from 20 to 60 turns... How
much inductance would we expect the coil to have - correct answer ✔✔20 squared= 400
60 squared= 3,600
3,600/400=9
What do we call the time interval in seconds (or fractions of a second) that it takes for a coil to
experience a 63.2% increase (or decrease) in current flow? - correct answer ✔✔1 time constant
What is the R-L time constant of a coil with 200 millihenries of inductance and 400 ohms of resistance?...
How long would it take for current through this coil to increase from zero to maximum ( or decrease
from maximum to zero) - correct answer ✔✔T=L/R (.2H/400 ohms= 500uS x 5TC= 2.5mS
Alternating current is defined as current which is periodically changing in ______, while continuously
changing in ______ - correct answer ✔✔Direction and Amplitude
The maximum value of an AC sine wave voltage is called the ____ value - correct answer ✔✔Peak
Unless otherwise specified, any values given for current or voltage in an ac circuit are assumed to be the
_____ or _____ value, which is equal to ______% of the peak value. - correct answer ✔✔Effective, RMS,
70
The number of complete cycles which are developed by alternator in a given unit of time is known as the
alternator's output - correct answer ✔✔Frequency
The amount of time needed to generate one cycle of AC is called the - correct answer ✔✔Period
How does the number of poles on the rotor of an alternator affect the output frequency of the unit -
correct answer ✔✔Directly proportional ( more poles, higher frequency at the same RPM)
How does the RPM of the rotor of an alternator affect the output frequency of the unit? - correct answer
✔✔Directly proportional (Higher RPM, higher frequency with the same number of poles)
What is the instantaneous value of voltage of a 200 volt peak sine wave at 30 degrees - correct answer
✔✔200 x Sin(30)= 100 volts
What is the instantaneous value of voltage of a 200 volt peak sine wave at 90 degrees - correct answer
✔✔200 x Sin(90) = 200 volts
What is resistance - correct answer ✔✔Is the opposition to current flow
, What is inductance - correct answer ✔✔Is the property of an inductor by which a change in current
induces a voltage in both itself and nearby conductors
What units are used to measure inductance - correct answer ✔✔Henries (H or h)
How much inductance does a coil have if it induces 5 volts into itself when current is changing at a rate
of 100 amps per second? - correct answer ✔✔5v/100 amps= 50mH
What does L stand for - correct answer ✔✔Inductance
What does N stand for - correct answer ✔✔Number of turns
What does A stand for - correct answer ✔✔core area
What does U stand for - correct answer ✔✔Core Permeability
What does I stand for - correct answer ✔✔Coil Length
If we were to increase the number of turns of wire on a 10 microhenry coil from 20 to 60 turns... How
much inductance would we expect the coil to have - correct answer ✔✔20 squared= 400
60 squared= 3,600
3,600/400=9
What do we call the time interval in seconds (or fractions of a second) that it takes for a coil to
experience a 63.2% increase (or decrease) in current flow? - correct answer ✔✔1 time constant
What is the R-L time constant of a coil with 200 millihenries of inductance and 400 ohms of resistance?...
How long would it take for current through this coil to increase from zero to maximum ( or decrease
from maximum to zero) - correct answer ✔✔T=L/R (.2H/400 ohms= 500uS x 5TC= 2.5mS
