Final Unit Test Flashcards
what is the phase relationship between current and voltage in an inductor for an ac circuit
voltage leads current by 90 degrees
x is
reactance in ohms
how does a capacitor differ from a resistor
a capacitor does not dissipate any energy as a resistor does, it only stores it during a portion of the ac cycle and returns it to the source during another portion of the cycle
inductive reactance and capacitive reactance both ______ current
Both appose current.
L
inductance in hennrys
reactive power
VARs - the product of volts and amps that are 90 degrees our of phase with each other.
pf formula
(W/VA)(100)
how to find total inductance in series?
sum of the inductors
the power factor of a RLC circuit is the ratio of
true power to apparent power written as a percentage
pf
power factor
What two factors determine inductive reactance of an inductor
frequency and inductance
in a purely resistive circuit voltage and current are ________.
in phase
as frequency increases inductive reactance _______.
increases
in a series LC circuit the voltage drop across the inductor ______ current by ______ degrees
leads , 90
reactive power is measured in
VARs
formula for inductive reactance
Xl = 2πFL
F
frequency in Hz
in a series LC circuit the voltage drop across the capacitor ____ current by _____ degrees
lags, 90
apparent power
VA - the value found if circuit voltage and current are multiplied together
how do you find total capacitance in parrallel
sum of the capacitors
a capacitor ______ dc but allows a ________ current to pass because of the _______ voltage.
blocks, changing, changing
in a purely inductive circuit voltage and current are?
90 degrees out of phase
when the voltage of a series RL circuit is increased impedance will
stay the same
as frequency increases capacitive reactance_______.
decreases
how do you find total capacitance in series?
use the reciprocal equation
capacitive reactance formula
1/(2πFC)
What factors determine the capacitive reactance of a capacitor
frequency, capacitance
Xl
inductive reactance
true power is measured in
watts
what is the phase relationship between current and voltage in a capacitor for and ac circuit
current leads voltage by 90 degrees
the higher the power factor percentage the more______ a circuit opperation
efficient
Xc is
capacitive reactance
va
volts amps
Z
impedance in ohms
in a purely resistive circuit the phase shift between voltage and current is
0 degrees
as frequency is increased in an RC series circuit total impedance will
decrease
apparent power is measured in
VAs
vars
volts amps resistance
in a series RL circuit voltage and current are?
our of phase somewhere between 0 and 90 degrees
capacitors ________ a change in voltage
oppose
true power
measured in watts and equal to the value of apparent power when current and voltage are in phase
when frequency _______ resistance ________.
raise, raise
