PHEP 17 Flashcards
What best defines a cycle
two alternations, one in each direction
How many times larger is the max voltage value than the effective voltage value
0.707
what is another name for effective values
root mean square value
Does an AC amp produces heat at the same rate as a DC amp
yes
what is the direction of a vector indicated by
a line segment and arrow
what is the magnitude of a vector indicated by
length of line
in what direction is positive rotation of a vector
counter clockwisewha
what effect does self induced voltage have on applied voltage
it opposes it and reduces effectiveness
what variables determine inductive reactance
2pi constant, frequency, inductance
what is the relationship between current and applied voltage in a purely inductive circuit
current lags 90 degrees
What are the two factors that limit current in an inductive circuit?
inductive reactance and resistance
in a purely inductive reactant and resistant circuit what is the current applied voltage relationship
current lags by 45 degrees
what are the units of capacity
farrads
what is power factor
ratio of true power to apparent power
AC meters and instruments are designed to read _____ voltage and currents.
Effective.
The effective values of voltage and current are equal to the maximum values multiplied by?
.707
The three factors that limit the flow of current in an AC circuit are?
- Resistance
- Inductive reactance
- Capacitive reactance
In a pure resistance circuit, voltage and current are?
In phase.
In an AC circuit, what represents total Opposition to current and what is the symbol?
Impedance, Z
What is the symbol for inductive reactance?
XL
Whats used to determine inductive reactance?
The frequency and the amount of inductance in a circuit.
What does ELI ICE represent?
ELI= voltage leads current (inductance) ICE= current leads voltage (capacitve)
The letters represent the symbols for voltage, current, inductance, capacitance.
Whats the relationship of voltage and current in a pure inductive circuit?
Voltage leads current by 90 degrees.
Capacitive reactance varies inversely with?
The frequency and the size of the capacitor.
In a pure capacitive circuit, voltage and current’s relationship is?
out of phase 90 degrees, with current leading.
What does VARs stand for?
Volt-ampere-reactive
The power factor is equal to the cosine of the?
angle of phase difference between voltage and current.
What is the measurement of the primary harmonic?
60hz
What increments do harmonics go by?
60
How can you reduce the third harmonic?
By connecting a set of winding’s in a transformer in delta.
Inductive reactance varies ______ with frequency.
Directly
Capacitive reactance varies _______ with frequencty
Inversely
Resonance is when?
Inductive reactance and capacitive reactance in a circuit cancels each other out and leaves only resistance.
A 60-cycle AC current reverses its direction ______ times per second.
120
