delmar section 7
Two capacitors, a 20 μF and a 30 μF, are connected in series. What is the total capacitance?
12 μF
A series RC circuit contains two resistors and two capacitors. The resistors are 82 Ω and 47 Ω. The capacitors have capacitive reactances of 80 Ω and 50 Ω. What is the total impedance?
183.14 Ω
In an RC parallel circuit, ET = 277 V, R = 82 kΩ, and XC = 33 kΩ. What is the apparent power?
2.51 VA
Two capacitors, a 20 μF and a 30 μF, are connected in series to a 400-Hz source. What is the total capacitive reactance?
53.05 Ω
What is the reactance of a 10 pF capacitor when the applied frequency is 30-Hz?
530.52 Ω
A series RC circuit contains two resistors and two capacitors. The resistors are 68 Ω and 56 Ω. The capacitors have capacitive reactances of 66 Ω and 33 Ω. The applied voltage is 240 V. What is the voltage drop on the 56 Ω resistor?
84.70 V
Color bands and dots on a dipped tantalum capacitor determine the value, tolerance, and voltage.
True
Counter voltage presented by a capacitor is called _____.
capacitive reactance
n what unit is the capacitance value given for a dipped tantalum capacitor?
picofarads
A capacitor is constructed by separating two metal conductors known as _____ with an insulating material known as a(n) _____.
plates; dielectric
When resistance and capacitive reactance are 90° degrees out of phase with each other, they form a right triangle. What is the impedance?
the hypotenuse
ER represents voltage drop across the resistor.
true
In a series RC circuit, ET = 240 V, R = 40 Ω, and XC = 30 Ω. What is EC?
144v
Two capacitors, a 20 μF and a 30 μF, are connected in parallel. What is the total capacitance?
50 μF
In an RC parallel circuit, ET = 240 V, R = 1000 Ω, and XC = 1500 Ω. What is the apparent power?
69.23 VA
Two capacitors, a 20 μF and a 30 μF, are connected in parallel to a 400-Hz source. What is the total capacitive reactance?
7.96 Ω
Which of these formulas would be used to calculate reactive power?
B
As the resistor is charged, an impressed voltage is developed across its plates as an electrostatic charge is built up.
false
The procedure for solving a resistive-capacitive series circuit is the exact same as for solving for a resistive-inductive series circuit.
false
The quality of a capacitor is generally very low.
false
In an RC parallel circuit, the voltage across the resistor and the voltage across the capacitor are _____.
in phase
Capacitors are used extensively in electronic circuits for control of frequency and pulse generation.
true
In a series RC circuit, total impedance is a combination of resistance and capacitive reactance.
true
Power factor can be calculated by dividing any resistive value by its like total value.
true
Reactive power in a circuit can be calculated in a manner similar to that used for watts except that reactive values of voltage and current are used instead of resistive values.
true
Temperature coefficients are listed in parts per million per degree Celsius.
true
The apparent power, true power, and reactive power form a right triangle in an RC parallel circuit.
true
The countervoltage in a capacitive reactance is similar to the countervoltage produced by an inductor.
true
Variable capacitors normally have a dielectric of _____.
air
What is the unit for capacitive reactance?
ohm
In a series RC circuit, ET = 240 V, R = 150 ?, and XC = 270 ?. What is the reactive power?
163 VARs
A capacitor is connected to a 240V supply. An ammeter indicates 3 A. What is the capacitive reactance of the capacitor?
80Ω
When the power factor and apparent power are known, the true power can be calculated for an RC parallel circuit.
true
When the total impedance of the circuit is known, the total current flow can be calculated.
true
How are small electrolytic capacitors generally tested for shorts?
with an ohmmeter
What is the symbol for capacitive reactance?
xc
Two capacitors, a 20 μF and a 30 μF, are connected in series to a 60-Hz source. What is the total capacitive reactance?
221.04 Ω
In an RC parallel circuit, ET = 480 V, R = 50 kΩ, and XC = 47 kΩ. What is the reactive power?
4.90 VARs
Two capacitors, a 20 μF and a 30 μF, are connected in parallel to a 60-Hz source. What is the total capacitive reactance?
53.05 Ω
Three capacitors, a 12 μF, a 20 μF and a 30 μF, are connected in series. What is the total capacitance?
6 μF
Three capacitors, a 12 μF, a 20 μF and a 30 μF, are connected in parallel. What is the total capacitance?
62 μF
Which of these formulas is used to calculate capacitance?
A
Which is the formula for finding capacitance?
B
In a series RC circuit, apparent power can be calculated by _____.
ET × I
When a capacitor is connected to an AC circuit, current appears to flow through the capacitor.
True
Of the different power values in an RC circuit, which is known as apparent power?
VA
The power in a capacitor is reactive power. What is the unit for reactive power?
VAR
In the formula Q = C x V, what does Q stand for?
charge in coulombs
Dividing a circuit's total applied voltage by the total impedance results in the total _____.
current
EC represents capacitive reactance.
false
In an RC parallel circuit, voltage across all branches do not need to be the same.
false
There is true power produced in a pure capacitive circuit.
false
The capacitive reactance of a capacitor is _____ proportional to frequency.
inversely
In a pure capacitive circuit, the current _____ the applied voltage by _____.
leads; 90°
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
Polarized capacitors _____.
must be used with DC only
The _____ of a circuit is the cosine of the phase angle.
power factor
The voltage rating of a capacitor _____.
should never be exceeded
On a ceramic capacitor, what does the wide band indicate?
temperature coefficient
In an RC parallel circuit, how is circuit power factor determined?
the ratio of true power and capacitance
Because the current flow in a pure capacitive circuit leads the applied voltage by 90°, the voltage and current have the same polarity for half the time during one cycle and have opposite polarities the other half of the time.
true
Which of these formulas would be used to calculate impedance?
D
Resistive-capacitive series circuits are similar to resistive-inductive series circuits.
true
Which of these formulas would be used to calculate power factor?
D
A charge curve for a capacitor is divided into _____ time constants.
five
A temperature coefficient that is __________ indicates the capacitor will decrease its capacitance with a decrease in temperature.
negative
By how many degrees is the voltage and current out of phase with each other when a circuit of both resistance and capacitance is connected to an AC circuit?
between 0° and 90°
When calculating an RC parallel circuit value, what does IR represent?
current flow through the resistor
Another type of polarized capacitor is the trimmer capacitor.
false
In a capacitive circuit, the voltage leads the current by 90 electric degrees.
false
The power factor is the sine of angle theta.
false
With the JAN standard of capacitor markings, the fourth dot indicates classes A to E of temperature and leakage coefficients.
false
When the voltage and current have _____ polarities in a pure capacitive circuit, the capacitor is discharging and the energy is returned to the circuit.
opposite
In the quality of a capacitor formula, what is represented by VARs?
reactive power
The power factor is the ratio of true power to apparent power.
true
The power required to charge the capacitor in a pure capacitive circuit is returned to the circuit when the capacitor discharges.
true
The total impedance is the total current-limiting element in the circuit.
true
When a circuit containing both resistance and capacitance is connected to an AC circuit, the voltage and current could be out of phase with each other at 63°.
true
While the farad is the basic unit of capacitance, it is seldom used because it is an extremely large amount of capacitance.
true
What does ER represent?
voltage drop across the resistor
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?
66.32 Ω
When a capacitor is connected to an AC circuit, the __________ charges one plate of the capacitor positive and the other plate negative.
ac generator
n a series circuit, the current-limiting elements must be _____________.
added
In a capacitor, the voltage difference between the plates controls the _____.
amount of dielectric stress
7349Which is the formula for finding the quality of a capacitor?
c
Which of these formulas is used to calculate impedance of the circuit?
c
The dielectric test set contains a variable voltage control, a voltmeter, and a microammeter.
true
Which of these formulas is used to calculate capacitive current?
B
If a(n) ____________ were placed in an AC circuit, it would indicate a continuous flow of current, giving the appearance that current is flowing through the capacitor.
ammeter
Three capacitors, a 12 μF, a 20 μF, and a 30 μF, are connected in parallel to a 60-Hz source. What is the total XC?
442.09 Ω
Three capacitors, a 12 μF, a 20 μF, and a 30 μF, are connected in series to a 60-Hz source. What is the total XC?
442.09 Ω
In an RC parallel circuit, ET = 120 V, R = 47 kΩ, and XC = 27 kΩ. What is IT?
5.13 mA
n an RC parallel circuit, the supply voltage is 120 V, 60 Hz. The resistance is 40 Ω and the capacitive reactance is 30 Ω. What is the capacitance of the capacitor?
88.42 μF
In an RC parallel circuit, the current flow through the capacitor will lead both the resistive current and applied voltage by _____.
90°
The quality of a capacitor is found by Q = _____.
R/XC
When a capacitor is connected in a circuit with a resistor, the amount of time needed to charge the capacitor is called the _____.
RC time constant
When a circuit containing both resistance and capacitance is connected to a ______, the voltage and current will be out of phase with each other.
ac circuit
In an RC parallel circuit, ET = 120 V, R = 300 Ω, and XC = 400 Ω. What is P?
36W
Which of these formulas would be used to calculate voltage drop across the resistor?
C
The _______________ indicates the amount of capacitance change with temperature.
Temperature Coefficient temperature coefficient temp coefficient Temp Coefficient
