ACL2
Voltage drop ( resistor ) equation
E_R_ = I_T_ * R
In a parallel RL circuit, the voltage across each branch is the same.
True
The ratio of a coil's inductive reactance to resistance (X_L_ / R) is referred to as the coil's ? whose symbol is ? .
quality factor / Q 1Q7
True or False Coils do not have resistance.
False Note: Coils are wound of wire, and all wire has some resistance. The correct answer is 'False'. 1Q6
A circuit has a resistor and a capacitor connected in series and operating at a certain frequency. If the frequency is increased, the current ? .
increases 2Q13
In a series RL circuit, power delivered by the source is apparent power.
true 4Q19
The power factor (PF) is a ratio of the ? power to ? power.
true / apparent 1Q22
The voltage drop across a resistor in a circuit can be determined by the formula ?.
E_R_ = I_R_ * R 1Q18
In a parallel RL circuit, power delivered by the source is apparent power.
True 4Q20
In a parallel circuit, IR and IL must be added vectorially to find the total current.
True 4Q8
A circuit has a resistor and a capacitor connected in series and operating at a certain frequency. If the frequency is increased, the capacitive reactance ? .
decreases 2Q17
Regarding a parallel RL circuit where the frequency is increased: X_L_ would ?
increase 4Q17
if the frequency is increased in a series AC circuit containing a resistor and an inductor. The resistance will ? .
remain the same 1Q32
The angular displacement by which the voltage and current are out-of-phase with each other is referred to as ? .
the angle theta 1Q25
Questions missing from this reveiw
4Q1 and 11
The voltage drop across an inductor in a circuit can be determined by the formula
E_L_ = I_L_ * X_L_ 1Q18
Inductive reactance of a circuit is directly proportional to ? . I. current II. frequency III. inductance IV. resistance V. voltage
II % III 1Q11
Given E = 120 V f = 60 Hz parallel branches containing -R = 30 ohms -X_L_ = 40 ohms Find I_R_ = ? I_L_ = ? I_T_ = ? Z = ? PF = ? Angle theta = ?
I_R_ = 4.00 A b/c E_R_ = E_L_ = E_R_ = 120 V I_R_ = E_R_ / R i_R_ = 120 / 30 I_R_ = 4 I_L_ =3.00 A b/c I_L_ = E_L_ / X_L_ I_L_ = 120 / 40 I_L_ = 3 I_T_ = 5.00 A I_T_ = sqrt( I^2_R_ + I^2_X_ ) I_T_ = sqrt (4^2 + 3^2) I_T_ = 5 A Z = 24 ohms b/c= E /I_T_ Z = 120 / 5 Z = 24 ohms PF = 80.0 % bc PF = I_R_ / I_T_ * 100 PF = 4 / 5 * 100 PF = 80 Angle theta = 36.9 degrees Angle theta = acos(I_R_ / I_T_ ) Angle theta = acos (4 / 5) Angle theta = 36.8 4Q10
For a series RC circuit in which R_1_ = 1000 ohms E_R1_ = 25 V E_C_ = 40V f = 200 hertz FIND I_T_ = ? C = ? E_T_ = ? PF = ?
I_R_ = I_C_ = I_T = E_R1_ / R_1_ =25/1000 =.025 E_T_ = sqrt( E_R_^2 + E_C_^2) E_T_ = sqrt( 25^2 + 40^2) E_T_ = 47.2 X_C_ = E_C_ / I_C_ X_C_ = 40/ .025 X_C_ = 1600 C = 1/2/pi/f/ X_C_ C = 1/2/pi/ 200 / 1600 C = .0000005 PF = E_R_ / E_T_ * 100 PF = 25/ 47.17 * 100 PF = 53% 2Q19
True or false To find the total impedance for a series RL circuit, vector addition must be used.
True 1Q14
A series circuit has a large R and small Xc. The phase angle is close to 0°.
True 2Q12
Power factor is generally expressed as a(n) ? .
percentage 1Q23
What is the total capacitance of a series circuit w/ R_1_ = 7 ohms R_2_ = 4 ohms C_1_ = .3 microFarads C_2_ = .2 microFarads C_3_ = .1 microFarads
C_T_ = 55nF C_T_ = 1/ ((1/C_1_) + (1/C_2_) + (1/C_3_)) 2Q5
What is the power factor equation?
PF = (P_true_ / P_app_) * 100 1Q24
Apparent Power equation
P_Apparent_ = E_T_ * I_T_
When the inductance of a series RL circuit increases, θ increases.
True
A resistor and an inductor are connected in parallel. What is the phase relationship between the two voltages?
0 degrees (in-phase) 4Q3
Using the formula: Z = ( R * X_L_) / sqrt( R^2 * X_L_^2 ) Solve for Z in the following: E_app_ = 6V F = 400Hz Branch 1 = R_1_ = 470 ohms Branch 2 = L = 107 mH
233.32 ohms b/c X_L_ = 2 * 3.14 * 400 * 0.107 X_L_ = 268.78 ohms Z = given wherein R = 470 and X_L_ = 268.78 4Q26
A 480-volt circuit has an impedance of 60 ohms. What is the current?
8 A I = E / Z =480 / 60 = 8 A 1Q29
The current is the same at all points in a parallel RL circuit.
False
Regarding a parallel RL circuit where the frequency is increased: Z would ?
Increase 4Q17
Which is the correct formula for determining total inductance in a circuit containing three inductors in series?
L_T_ = L_1_ + L_2_ + L_3_ 1Q3
Reactive Power equation
P_Reactive_ = I_T_ * E_Xl_
Which is the correct formula for determining total resistance in a circuit containing three resistors in series?
R_T_ = R_1_ + R_2_ + R_3_ 1Q2
The ? of the angle theta (∠θ) in a power triangle is also the power factor.
cosine 1Q26
Both resistance and inductive reactance oppose current flow, and their combined opposition is called ? .
impedance 1Q12
Two resistors are connected in parallel. One has a current flow of 2 amperes and the other draws 4 amperes. What is the total current?
I_T_ = 6 A b/c I_T_ = I_R1_ + I_R2_ I_T_ = 2 + 4 I_T_ = 6 A 4Q5
if the frequency is increased in a series AC circuit containing a resistor and an inductor. The voltage drop across the inductor will ?.
increase 1Q32
In a series RL circuit, the vector sum of the currents equals the total current.
False note: There is only one current in a series circuit. 4Q18
What is the equation to find inductive resistance?
X_L_ = 2 * pi * f * L 1Q4
Given a series crkt in which I_T_ = 10 amps R_1_ = 6 ohms X_L_ = 10 ohms Would the current lag the applied voltage?
Yes 3Q2
Given a series circuit with one resistor (120 ohms) and one capacitor (80 ohms ) What is the impedance? What is the angle theta?
Z = sqrt (R^2 + X_L_^20 Z = sqrt (120^2 + 80^2) Z = 144 ohms Angle theta = arcosine ( R/Z) =arcosine (120/144.22) =34 degrees 1Q30
A series circuit has a large Xc and small R. The power factor is close to 100%.
False Note: The largest voltage drop occurs across the capacitive element in the circuit. 2Q11
True Power equation
P_True_ = I_T_ * E_R_
For a series RC circuit, the ? must be the same through all parts of the circuit.
current 2Q2
Impedance is measured in ? and is designated by ? .
ohms / Z 1Q13
When R and XL are present in a circuit, theta is somewhere between ? and ? .
0 degrees / 90 degrees 1Q27
A circuit has an applied voltage of 240 volts and draws 5 amperes. The power factor is 70%. What is the apparent power? The values calculated for this question will be used for additional questions.
1,200 VA b/c P_app_ = E_app_ * I_T_ P_app_ = 240 * 5 P_app = 1,200 4Q15
Solve for the impedance of the circuit shown by determining branch currents and total current using Ohm's Law. (Round the FINAL answer to two decimal places.) E_app_ = 6V F = 400Hz Branch 1 = R_1_ = 470 ohms Branch 2 = L = 107 mH
233.32 ohms I_R_ = E / R I_R_ = 6 / 470 I_R_ = 0.012765957 A I_L_ = E / X_L_ I_L_ = 6 / 268.78 I_L_ = 0.022322757 A I_T_ = sqrt ( I_R_^2 + I_L_^2 ) I_T_ = 0.025715271 A Z = E_T_/ I_T_ Z = 233.32 ohms
Questions missing from this review are
2Q6 and 2Q8
In this series circuit, the voltage drop across the resistor is 130 volts, and the applied voltage is 150 volts. What is the voltage drop across the coil? (Round the FINAL answer to one decimal place.)
74.8 V note: E_app_ = sqrt ( E_R_^2 + E_L_^2) E_L_ = sqrt ( E_app_^2 - E_R_^2) = sqrt (150^2 - 130^2 ) =q1974.8 V 1Q19
A circuit has an applied voltage of 240 volts and draws 5 amperes. The power factor is 70%. What is the true power?
840 W b/c P_true_ = E_T_ *I_T_ *PF P_true_ = P_app_ *PF P_true_ = 1,200 * 0.7 P_true_ = 840 W 4Q16
VARs represents the product of the volts and amps that are ? out-of-phase with each other.
90 degrees 1Q21
The current through the resistive branch of a parallel circuit is ? out-of-phase with the current through the inductive branch.
90 degrees 4Q7
In a circuit containing only inductance (if this is possible), what is the phase relationship between the current and the applied voltage?
90° out-of-phase, lagging 1Q8
Given a power triangle A = horizontal B = vertical C = diagonal Where do the following powers lie? Apparent = ? Reactive =? True = ?
Apparent = C Reactive = B True = A 2Q9
Given a power triangle, what units are the following expressed in? Apparent = ? Reactive = ? True = ?
Apparent = VA (volt-amperes) Reactive = VARs (volts-amperes reactive) True = W (watts) 2Q9
Voltage drop ( coil) equation
E_Coil_ = I_T_ * E_XL_
When the resistance of a series RL circuit is increased, the circuit becomes more inductive.
False Note: Current is uniform in a series circuit; as the resistance is increased, the voltage drop across the resistor increases and it becomes a larger portion of total voltage. 4Q22
When analyzing the current in a parallel RL circuit with a large R and a small value of XL, the phase angle theta is close to 0°.
False Note: In parallel, voltage is constant; therefore, the inductive branch would have a larger current than the resistive branch and the phase angle would be closer to 90° 4Q9
When solving a series RC circuit, the voltage is the reference.
False Note: In a series circuit, current is the only circuit quantity that remains the same through all parts of the circuit and therefore becomes the reference. 2Q3
True or False A resistor and an inductor are connected in parallel. The resistor draws 2 amperes and the inductance 4 amperes. The total current is 6 amperes.
False b/c The current values in parallel RL circuits cannot be added directly; the current in the resistor and the current in the inductor are 90° out-of-phase and must be added vectorially 4Q6
Given a series circuit with f_1_ = 1000Hz f_2_ = 2000Hz E_T_ = 6V Resistor (R = 470 ohms) Capacitor ( L = 107mH) FIND I_T@1000Hz = ? I_T@2000Hz = ?
I_T@1000 HZ = 7.31 mA b/c X_L-1000 HZ = 2pif_1_ * L =2pi 1000 * 0.107 =672.30 Z_1000-Hz = sqrt(R^2 + X_L-1000-Hz_^2 ) =sqrt( 470^2 + 672.3^2 ) =820.3 I_T@1000HZ = E_T_ / Z_1000-Hz_ ) =6/820.30 =.00731 I_T@2000 HZ = 4.21mA b/c X_L-2000-Hz = 2 pi f_@_ L =2pi 2000 * .107 =1344.6 Z_2000-HZ_ = sqrt(R^2 + X_L-2000-Hz_^2) =sqrt(470^2 + 1344.6^2) =1424.38 I_T@2000 HZ_ = E_T / Z_2000-Hz_ =6 / 1424.38 =.00421 A 1Q33 E_T_ / Z_2000-Hz_ =6
Given a series circuit with a capacitor (inductance = 10H) a resistor (R = 1500 ohms) supplied voltage is 120 V Frequency is 60 Hz. FIND Total current? Power Factor? Angle theta?
I_T_ = .0296, b/c X_L_ = 2pi *60 * 10 =3769.91 Z = sqrt (R^2 + X_L_^2) Z = 4057.37 I = V / Z = 120 / 4057.37 =.0296 PF = 37 % b/c =R / Z * 100 =1500 / 4057.37 / 100 = 37 Angle theta =68.3 degrees b/c acos ( R / Z) =acos (1500 / 4057.37) =68.3 degrees 1Q31
A series circuit contains 40 ohms of resistance (R) and 70 ohms of capacitive reactance (Xc). When 100 volts AC are applied, how much current flows? (Round the FINAL answer to two decimal places.)
I_T_ = 1.24 A b/c Z = sqrt( R^2 +X_C_^2 ) =sqrt( 40^2 + 70^2) = 80.82 I = E / Z =100/81 =1.24A 2Q10
What is the total resistance of a series circuit w/ R_1_ = 7 ohms R_2_ = 4 ohms C_1_ = .3 microFarads C_2_ = .2 microFarads C_3_ = .1 microFarads
R_T_ = 11 ohms R_T_ = R_1_ + R_2_ R_T_ = 7 + 4 =11
if the frequency is increased in a series AC circuit containing a resistor and an inductor. The applied voltage will ?.
Remain the same 1Q32
What is meant by the statement that the circuit is a RL circuit?
The circuit contains inductive reactance and resistance 1Q10
True or False A circuit that contains resistance and capacitance is called an RC circuit.
True 2Q1
The impedance of a parallel RL circuit is always less than the resistance or reactance of any one branch.
True 4Q12
True or False Using the impedance triangle is just one method of graphically showing how out-of-phase quantities can be added.
True Note: The triangle method only works for quantities that are 90° out-of-phase. 1Q15
When the resistance of a parallel RL circuit is increased, the circuit becomes more inductive.
True : Note: As the resistance increases, the result is less current in the resistive branch and the reactive current becomes a greater portion of the total current. 4Q21
Given a series circuit with... E_T_ = 30V f = 60 Hz R = 4700 ohms C = 470 nanoFarads FIND Z = ? I_T_ = ? E_R_ = ? E_C_ = ? PF = ?
X_C_ = 1/2/pi/f/C X_C_ = 1/2/pi/ 60 / .00000047 X_C_ = 5643.79 Z = sqrt(R^2 + X_C_^2^) Z = sqrt(4700^2 + 5643.79^2) I_T_ = E_T_ / Z I_T_ = 30 / 7344.55 E_R_ = I_T_ * R E_R_ = 0.0040846622896040 *4700 E_C_ = I_T_ * X_C_ E_C_ = 0.0040846622896040 *5643.79 E_C_ = 23.1 PF = R / Z * 100 PF = 4700 / 7344.55 * 100 PF = 63.99% 2Q20
Given a series circuit w/ E_T_ = 120 V f = 60 Hz R = 140 ohms C = 15 nanoFarads FIND X_C_ = ? Z = ? I_T_ = ? E_C_ = ? E_R_ = ? PF = ? Angle theta = ?
X_C_ = 1/2/pi/f/C X_C_ = 1/2/pi/60/ 0.000015 X_C_ = 176.84 ohms Z = sqrt(R^2+ X_C_^2) Z = sqrt(140^2 + 176.84^2) Z = 225.55 ohms I_T_ = E_T_ / Z I_T_ = 120 / 225..55 I_T_ = .532037 A E_C_ = I_T_ * X_C_ E_C_ = .5320371605675510 * 176.84 E_C_ = 94.1 V E_R_ = I_T_ * R E_R_ = .5320371605675510 *140 E_R_ = 74.5 V P_F_ = R / Z *100 P_F_ = 140/ 225.55 * 100 P_F_ = 62.1% Angle theta = acos( R / Z ) Angle theta = acos (140 / 225.55) Angle theta = 51.6 degrees 2Q18
Given a series circuit wherein I_T_ = 10A R_1_ = 6 ohms X_L_ = 10 ohms Find Z E_app_ E_L_ E_R_ PF Angle theta
Z = 11.66 ohms b/c Z = sqrt(R^2 + X_L_^2 ) Z = sqrt(6^2 + 10^2) E_app_ = 117 V E_app = I_T_ * Z E_app = 10 * 11.66 E_L_ = 60 E_L_ = 10 * 6 PF = 51% PF = R/ Z * 100 PF = 6/ 11.66 * 100 Angle theta = acos( R / Z ) Angle theta =acos ( 6 / 11.66) Angle theta = 59 degrees 3Q1
Given a series circuit wherein I_T_ = 3.5A Resistor = 40 ohms Capacitor = 60 ohms Find.... Z = ? E_R_ = ? E_C_ = ? E_T_ = ? P_react_ = ? P_true_ = ? P_app_ = ? PF = ? Angle theta = ?
Z = sqrt(R^2 + X_C_^2 ) =72.11 ohms E_R_ = I_T_ * R =140 V E_C_ = I_T_ * X_C_ =210 V E_T_ = I_T_ * Z =252.4 V P_react_ = I_T_ * E_C_ =735 VARS P_true_ = I_T_ * E_R_ = 490 W P_app_ = I_t_ * E_T_ =883.4 VA PF = R / Z * 100 =55.5% Angle theta = acos (R / Z) = 56.3 degrees 2Q7
In a parallel RL circuit, the ? can be computed by multiplying the line voltage by the line current.
apparent power 4Q13
One of the primary laws for series circuits is that the ? must be the same in any part of the circuit.
current 1Q17
In a series RL circuit, the ? are in-phase, and the ? are out-of-phase. In a parallel RL circuit, the ? are in-phase, and the ? are out-of-phase.
currents voltages voltages currents 4Q4
if the frequency is increased in a series AC circuit containing a resistor and an inductor. The current will ?
decrease 1Q32
if the frequency is increased in a series AC circuit containing a resistor and an inductor. The power factor will?
decrease 1Q32
if the frequency is increased in a series AC circuit containing a resistor and an inductor. The true power will ? .
decrease 1Q32
if the frequency is increased in a series AC circuit containing a resistor and an inductor. The voltage drop across the resistor will ?
decrease 1Q32
Regarding a parallel RL circuit where the frequency is increased: I_T_ would ?
decrease 4Q17
Regarding a parallel RL circuit where the frequency is increased: The phase angle would ?
decrease 4Q17
A circuit has a resistor and a capacitor connected in series and operating at a certain frequency. If the frequency is increased, the phase angle ? .
decreases 2Q14
A circuit has a resistor and a capacitor connected in series and operating at a certain frequency. If the frequency is increased, the impedance ? .
decreases 2Q16
if the frequency is increased in a series AC circuit containing a resistor and an inductor. The impedance will?
increase 1Q32
if the frequency is increased in a series AC circuit containing a resistor and an inductor. The inductive reactance will ?
increase 1Q32
if the frequency is increased in a series AC circuit containing a resistor and an inductor. The phase angle will?
increase 1Q32
Regarding a parallel RL circuit where the frequency is increased: The power factor would ?
increase 4Q17
A circuit has a resistor and a capacitor connected in series and operating at a certain frequency. If the frequency is increased, the power factor ? .
increases 2Q15
Refer to the formula XL = 2πfL. If L increases, XL ? , and if f increases, XL ? .
increases / increases 1Q5
Resistance is measured in ? and is designated by ? .
ohms / R 1Q13
Inductive reactance is measured in ? and is designated by ? .
ohms/ XL 1Q13
If a circuit contains ? , the current and the applied voltage will always be in-phase.
only resistance 1Q9
More resistance in a RL series circuit causes the vertical component of an impedance triangle to become relatively ? with a ? phase angle.
shorter / smaller 1Q28
The power factor in a parallel RL circuit is the ratio of ? to ? .
watts / volt amps 4Q14
