PHY112 FINAL QUESTIONS AND
ANSWERS 100% ACCURATE 2025
A series R-L-C circuit with a sinusoidal voltage source of angular frequency ω has a
total reactance X. If the frequency is doubled, the reactance becomes - ANSWER-none
of these.
A series R-L-C circuit has a sinusoidal voltage source of angular frequency ω. If the
frequency is doubled - ANSWER-the inductive reactance is doubled.
For the current to have its maximum value in a series R-L-C circuit, - ANSWER-ω =
1/(√LC).
In a series R-L-C circuit at resonance, - ANSWER-the total impedance has its minimum
value, which is equal to R.
A circuit has a resistance of 4.0Ω; a reactance, due to the capacitance, of 26Ω; and a
reactance, due to the inductance, of 17Ω. Find the impedance of the circuit. - ANSWER-
9.8 Ω
Imp = Z
The inductor in a radio receiver carries a current of amplitude 200 mA when a voltage of
amplitude 2.4 V is across it at a frequency of 1400 Hz. What is the value of the
inductance? - ANSWER-1.36 mH
w = 2pi(f)
L = V/iw = V/I(2pi(f))
VL = IXL = 2pi(F)(I)
A series circuit has a 50-Hz AC source, a 60-ohm resistor, a 0.50-H inductor, and a 10-
μF capacitor. The RMS current in the circuit is 2.2 A. The power factor of the circuit is
closest to - ANSWER-0.35.
P = cos(phi) = R/Z
w = 2piF
1) Find w
2) Find XL, XC
3) tan^-1 (X/R) = phi
4) cos phi = P
, Which of the phasor diagrams shown below represents a series RLC circuit driven at
resonance?
http://qm.riosalado.edu/Resources/phy/phy112/20140505/Quiz5_Q8.png.JPG -
ANSWER-3
A series ac circuit is shown below. The inductor has a reactance of 70 ohms and an
inductance of 210 mH. A 30-ohm resistor and a capacitor whose reactance is 120 ohms
are also in the circuit. The RMS current in the circuit is 2.0 A. The peak magnetic energy
in the inductor is closest to
http://qm.riosalado.edu/Resources/phy/phy112/20140505/Quiz5_Q9.png - ANSWER-
0.84 J.
Emax = 1/2(L)(Imax^2)
Imax = sqrt(2)(I)
A series ac circuit is shown below. The inductor has a reactance of 50 ohms and an
inductance of 240 mH. A 50-ohm resistor and a capacitor whose reactance is 140 ohms
are also in the circuit. The RMS current in the circuit is 1.2 A. The capacitor is changed
so that the circuit is in resonance. The voltage of the source is adjusted so that the RMS
current of 1.2 A is maintained. The new voltage amplitude of the source is closest to
http://qm.riosalado.edu/Resources/phy/phy112/20140505/Quiz5_Q10.png - ANSWER-
85 V
V = IZ
1. Find Z
2. Divide Z by sqrt(2)
3. Multiply by I
Unpolarized light with an original intensity Io passes through two ideal polarizers having
their polarizing axes turned at 120° to each other. After passing through the polarizers,
the intensity of the light is - ANSWER-1/8 Io.
First filter = 1/2 of light
Second = cos^2(theta)
Intensity = first*second
If a sinusoidal wave with intensity 10 W/m2 has an electric field of amplitude E, then a
20 W/m2 wave of the same wavelength will have an electric field of amplitude -
ANSWER-√2E.
Two lasers each produce 2 mW beams. The beam of laser B is wider, having twice the
cross-sectional area as the beam of laser A. Which of the following statements
concerning the beams is (are) accurate? - ANSWER-a. Both of the beams have the
same average power.
ANSWERS 100% ACCURATE 2025
A series R-L-C circuit with a sinusoidal voltage source of angular frequency ω has a
total reactance X. If the frequency is doubled, the reactance becomes - ANSWER-none
of these.
A series R-L-C circuit has a sinusoidal voltage source of angular frequency ω. If the
frequency is doubled - ANSWER-the inductive reactance is doubled.
For the current to have its maximum value in a series R-L-C circuit, - ANSWER-ω =
1/(√LC).
In a series R-L-C circuit at resonance, - ANSWER-the total impedance has its minimum
value, which is equal to R.
A circuit has a resistance of 4.0Ω; a reactance, due to the capacitance, of 26Ω; and a
reactance, due to the inductance, of 17Ω. Find the impedance of the circuit. - ANSWER-
9.8 Ω
Imp = Z
The inductor in a radio receiver carries a current of amplitude 200 mA when a voltage of
amplitude 2.4 V is across it at a frequency of 1400 Hz. What is the value of the
inductance? - ANSWER-1.36 mH
w = 2pi(f)
L = V/iw = V/I(2pi(f))
VL = IXL = 2pi(F)(I)
A series circuit has a 50-Hz AC source, a 60-ohm resistor, a 0.50-H inductor, and a 10-
μF capacitor. The RMS current in the circuit is 2.2 A. The power factor of the circuit is
closest to - ANSWER-0.35.
P = cos(phi) = R/Z
w = 2piF
1) Find w
2) Find XL, XC
3) tan^-1 (X/R) = phi
4) cos phi = P
, Which of the phasor diagrams shown below represents a series RLC circuit driven at
resonance?
http://qm.riosalado.edu/Resources/phy/phy112/20140505/Quiz5_Q8.png.JPG -
ANSWER-3
A series ac circuit is shown below. The inductor has a reactance of 70 ohms and an
inductance of 210 mH. A 30-ohm resistor and a capacitor whose reactance is 120 ohms
are also in the circuit. The RMS current in the circuit is 2.0 A. The peak magnetic energy
in the inductor is closest to
http://qm.riosalado.edu/Resources/phy/phy112/20140505/Quiz5_Q9.png - ANSWER-
0.84 J.
Emax = 1/2(L)(Imax^2)
Imax = sqrt(2)(I)
A series ac circuit is shown below. The inductor has a reactance of 50 ohms and an
inductance of 240 mH. A 50-ohm resistor and a capacitor whose reactance is 140 ohms
are also in the circuit. The RMS current in the circuit is 1.2 A. The capacitor is changed
so that the circuit is in resonance. The voltage of the source is adjusted so that the RMS
current of 1.2 A is maintained. The new voltage amplitude of the source is closest to
http://qm.riosalado.edu/Resources/phy/phy112/20140505/Quiz5_Q10.png - ANSWER-
85 V
V = IZ
1. Find Z
2. Divide Z by sqrt(2)
3. Multiply by I
Unpolarized light with an original intensity Io passes through two ideal polarizers having
their polarizing axes turned at 120° to each other. After passing through the polarizers,
the intensity of the light is - ANSWER-1/8 Io.
First filter = 1/2 of light
Second = cos^2(theta)
Intensity = first*second
If a sinusoidal wave with intensity 10 W/m2 has an electric field of amplitude E, then a
20 W/m2 wave of the same wavelength will have an electric field of amplitude -
ANSWER-√2E.
Two lasers each produce 2 mW beams. The beam of laser B is wider, having twice the
cross-sectional area as the beam of laser A. Which of the following statements
concerning the beams is (are) accurate? - ANSWER-a. Both of the beams have the
same average power.
