Electrical Prep 2A 19, 20, 21, 22, 23, 24, 25, 26 NCER
one-third the applied voltage
Each of three equal capacitors in series has:
False
IR represents current flow through the inductor.
ohm
What is the unit for capacitive reactance?
180°
Because inductive reactance and capacitive reactance are _____ out of phase with each other, they subtract from each other in an AC circuit.
True
IL(Load 1) represents the line current to Load 1 (resistive).
75%
In a balanced three-phase system, the conductors need to be only about _____ the size of conductors for a single-phase, two-wire system of the same kilovolt-ampere (kVA) rating.
False
In a capacitive circuit, the voltage leads the current by 90 electric degrees.
bandwidth
In a parallel LC circuit, the difference in frequencies above and below resonance at which impedance is 0.707 of the maximum is called the _____ of the circuit.
square root of three
In a wye-connected system, the line voltage is higher than the phase voltage by a factor of _____.
90°
In an RC parallel circuit, the current flow through the capacitor will lead both the resistive current and applied voltage by _____.
in phase
In an RC parallel circuit, the voltage across the resistor and the voltage across the capacitor are _____.
Q = ITANK / ILINE
For parallel resonant circuits, the correct formula relating ITANK, Q, and ILINE is _____.
bandwidth
The difference between the two frequencies at which the current is 0.707 of the maximum current value is the _____.
current; voltages
In an RLC series circuit, _____ is the same through all components and the _____ are out of phase.
True
In an RLC series circuit, as frequency increases, inductive reactance increases and capacitive reactance decreases.
three
In calculating apparent power (VA) in a three-phase circuit, the phase values of voltage and current are multiplied by _____.
530.52Ω
What is the reactance of a 10 pF capacitor when the applied frequency is 30 Hz?
current flow through the inductor
When calculating values in an RLC parallel circuit, what does IL represent?
reactive power of the capacitor
When calculating values in an RLC parallel circuit, what does VARSC represent?
high-Q components
When determining bandwidth, what components result in a sharp increase and decrease of current?
True
When using vector addition for inductive reactance and capacitive reactance, the smaller value is eliminated.
True
The current flowing through a pure resistive element in an RLC parallel circuit will be in phase with the applied voltage.
True
The impedance of an RLC parallel circuit is the reciprocal of the sum of the reciprocals of the legs.
True
The impedance of the RLC series circuit is the sum of resistance, inductive reactance, and capacitive reactance.
VAR
The power in a capacitor is reactive power. What is the unit for reactive power?
current with respect to time
The self-induced voltage across an inductance is produced by a change in:
wye
The three-phase connection in which one end of each of the windings are connected together is called a(n) _____ connection.
66.32 Ω
Three capacitors, a 12 μF, a 20 μF, and a 30 μF, are connected in series to a 400 Hz source. What is the total XC?
221.04 Ω
Two capacitors, a 20 μF and a 30 μF, are connected in series to a 60 Hz source. What is the total capacitive reactance?
line voltage of the load
What does EL(Load) represent?
phase current of the load
What does IP(Load) represent?
farad
What is the basic unit of capacitance?
10A
What is the current flow in a purely resistive AC circuit if the resistance is 15 ohms and the voltage is 150V?
40Hz
What is the frequency of an AC waveform that completes 20 cycles per half second?
2:1
What is the step-down turns ratio of a transformer with 200 turns in the primary and 100 turns in the secondary?
F
What letter symbolizes the farad?
False
When Ohm's law is applied to the RLC series circuit values, the voltage drops developed across the inductor or capacitor can be lower than the applied voltage.
AC
When a capacitor is connected to a(n) _____ circuit, current appears to flow through the capacitor.
the same
When an AC circuit contains elements of resistance, inductance, and capacitance connected in parallel, what is the voltage dropped across each element?
henrys
When calculating resonant frequency, in what units is inductance measured?
quality of bandwidth
When determining bandwidth, what does Q represent?
Determine the reactive power of the circuit.
When determining the amount of capacitance needed to correct power factor, what is the first step?
ET × I
In a series RC circuit, apparent power can be calculated by _____.
multiplying apparent power by the power factor
In a three-phase circuit, the true power (watts) is found by _____.
True
In a three-phase connection, what is the voltage measured across a single winding?
phase voltage
In a three-phase connection, what is the voltage measured across a single winding?
cancel
Inductive and capacitive reactance _______ each other at resonance.
45
A 30-microfarad capacitor is in parallel with a 15-microfarad capacitor. The total capacitance is:
75.79 Ω
A 35 μF capacitor is connected to a 60-Hz, 120 V supply. What is the XC of the capacitor?
dielectric
A HIPOT is a test set used to test capacitor _____.
175V
A circuit has a peak voltage of 275V. What is the average voltage value?
exponential
Capacitors charge and discharge at a(n) _____ rate.
resistance to capacitance
In an RC parallel circuit, the amount of phase angle shift depends on the ratio of the amount of _____.
square wave
One type of non-sinusoidal waveform is the:
power factor
The _____ of a circuit is the cosine of the phase angle.
Temperature coefficient
The _______________ indicates the amount of capacitance change with temperature.
XL = 2πfL
The formula for inductive reactance is:
150%
The horsepower rating of three-phase motors and the kilovolt-ampere rating of three-phase transformers are about _____ greater than for single-phase motors or transformers with a similar frame size.
120°
Three-phase voltages are _____ out of phase with each other.
parallel
To correct the power factor to 100%, an equal amount of capacitive VARs would be connected in _____ with the motor.
frequency of resonance
What can be determined when the values of inductance and capacitance are known?
air
Variable capacitors normally have a dielectric of _____.
10,000 Ω
A parallel circuit at resonance has ITANK = 1.00 A, ILINE = 0.05 A, Q = 20, and a voltage across the tank of 500 V. What is the impedance of the tank?
greater than the true power
According to the power triangle, the apparent power is:
electrostatic charge
Energy in a capacitor is stored as a(n) _____.
VARs
If a three-phase load is a pure reactive load, then the power calculated has units of _____.
75VAC
If a transformer has 200 turns in the primary, 100 turns in the secondary, and 150VAC applied to the primary, the voltage across the secondary is:
leading
If an RLC parallel circuit contains more capacitive VARs than inductive VARs, the circuit has a _____ power factor.
lagging
If an RLC series circuit contains more inductive VARs than capacitive VARs, the circuit has a _____ power factor.
never falls to zero
In three-phase power systems, the delivered power _____.
Tank
LC parallel circuits are often referred to as _______________ circuits.
wye
Line current and phase current are the same in the _____ configuration.
must be used with DC only
Polarized capacitors _____.
electrolytic
Polarized capacitors are also known as _____ capacitors.
apparent; true
Power factor (PF) is the ratio of the _____ power to the _____ power.
line current
The alternator must supply the _____ for each of the loads.
should never be exceeded
The voltage rating of a capacitor _____.
6.42 Ω
Three capacitors, a 12 μF, a 20 μF, and a 30 μF, are connected in parallel to a 400 Hz source. What is the total XC?
True
In a series RC circuit, total impedance is a combination of resistance and capacitive reactance.
opposite
When the voltage and current have _____ polarities in a pure capacitive circuit, the capacitor is discharging and the energy is returned to the circuit.
100 V
A delta connected set of windings has a phase voltage of 100 V. What is the line voltage?
transformer
A device that uses electromagnetic induction to transfer electrical energy from one circuit to another is a(n):
delta
A three-phase connection in which three separate inductive loads have been connected together is a(n) _____ connection.
subtract
Because inductive reactance and capacitive reactance are 180° degrees out of phase with each other, they __________from each other in an AC circuit.
increases
If the area of the plates of a capacitor is increased, the amount of capacitance:
leading
If the current leads the voltage in an RLC series circuit, the power factor is referred to as _____.
lagging
If the voltage in an RLC series circuit is ahead of the current, the power factor is referred to as _____.
180° out of phase
In a circuit containing a capacitor, the impressed voltage is _____ with the applied voltage.
line voltage
In a three-phase connection, what is the voltage measured between the lines?
True
In an RLC parallel circuit, the phase angle difference between the applied voltage and the total current is determined by the ratio of resistance, inductance, and capacitance connected in parallel.
resonance
In an RLC series circuit, the point at which X L and X C are equal is called _____.
voltage
In an RLC series circuit, the ratio of resistance, inductance, and capacitance determines how much the applied _____ leads or lags the circuit current.
electrolytic
In some capacitors, there is a small amount of current that flows from one plate, through the dielectric material to the other plate. This current is called _____ current.
leakage
In some capacitors, there is a small amount of current that flows from one plate, through the dielectric material to the other plate. This current is called _____ current.
delta
Line voltage and phase voltage are the same in the _____ connection.
VA
Of the different power values in an RC circuit, which is known as apparent power?
induced high voltage
Opening the secondary circuit of a current transformer under load will cause a dangerous level of:
True
Subtraction of the inductive reactance and capacitive reactance in an RLC series circuit, permits the impedance of the circuit to become less than either or both of the reactances.
False
The current flowing through a pure inductive element leads the applied voltage by 90 electrical degrees.
