Deck 22: Reflection and Refraction of Light: Part A

Question 1

In some countries the AC frequency is 50 Hz.What is the time interval for one cycle at this frequency?

A) 0.0050 s
B) 0.020 s
C) 2 s
D) 50 s

Answer 1

0.020 s

Question 2

An AC voltage source,with a peak output of 120 V,results in dissipation of energy in a resistor at rate of 50.0 W.What is the value of the resistance?

A) 100 Ω
B) 120 Ω
C) 144 Ω
D) 72.0 Ω

Answer 2

144 Ω

Question 3

When a 50-μF capacitor is attached to an AC source,its capacitive reactance is 60 Ω.If instead a 200-μF capacitor is attached to the same source,what will be its capacitive reactance?

A) 80 Ω
B) 15 Ω
C) 30 Ω
D) 120 Ω

Answer 3

15 Ω

Question 4

In an AC series circuit the inductive reactance is 150 Ω and the frequency is 100 Hz.What is the inductance in the circuit?

A) 740 mH
B) 80 mH
C) 500 mH
D) 240 mH

Question 5

An AC circuit consists of a 60-Hz source,a 200-Ω resistor,and a 1.06-H inductor,all in series.What is the impedance of this circuit?

A) 400 Ω
B) 280 Ω
C) 600 Ω
D) 450 Ω

Question 6

The output voltage of an AC generator is of the form V = V​₀ sin(2πft).A typical frequency in household circuits is 60 Hz.Using radians for angular measure in this equation,what is the factor 2πf in radians per second for this frequency?

A) 2π
B) 120
C) 377
D) 60

Question 7

An AC voltage source,with a peak output of 200 V,is connected to a 25-Ω resistor.What is the effective (or rms)current in the circuit?

A) 2.8 A
B) 5.7 A
C) 4.0 A
D) 2.0 A

Question 8

At what frequency does a 0.32-H inductor have the same reactance as a 0.22-μF capacitor?

A) 3.8 × 10³ Hz
B) 3.6 × 10⁵ Hz
C) 24 Hz
D) 6.0 × 10² Hz

Question 9

In an AC series circuit the capacitive reactance is 253 Ω and frequency is 100 Hz.What is the capacitance?

A) 6.29 μF
B) 8.0 μF
C) 50.0 μF
D) 3.2 μF

Question 10

The peak voltage of an AC source is 400 V.What is the rms voltage?

A) 100 V
B) 200 V
C) 141 V
D) 283 V

Question 11

What is the effective (rms)current value for an AC current with an amplitude of 20 A?

A) 28 A
B) 7.1 A
C) 3.1 A
D) 14 A

Question 12

The frequency in an AC series circuit is halved.By what factor does this change the capacitive reactance?

A) 1/2
B) 4
C) 1/4
D) 2

Question 13

An AC voltage source,with a peak output of 200 V,is connected to a 25-Ω resistor.What is the rate of energy dissipated due to heat in the resistor?

A) 566 W
B) 400 W
C) 800 W
D) 200 W

Question 14

A 400-Ω resistor and a capacitor are connected in parallel across a 300-Hz source.If the amplitude of the current in the resistor is equal to that in the capacitor,what is the value of the capacitance?

A) 1.33 × 10^-6 F
B) 0.750 × 10^-6 F
C) 10.6 × 10^-6 F
D) 0.212 F

Question 15

An AM radio tuning circuit has a coil with an inductance of 4.00 mH and a capacitor set at 7.50 × 10−⁶ μF.What frequency will it detect?

A) 1520 kHz
B) 919 kHz
C) 550 kHz
D) 750 kHz

Question 16

A 400-Ω resistor and an inductor are connected in parallel across a 300-Hz source.If the amplitude of the current in the resistor is equal to that in the inductor,what is the value of the inductance?

A) 0.212 H
B) 0.666 H
C) 1.33 × 10^-6 H
D) 0.333 H

Question 17

A series LC circuit in a radio is in resonance with AM 1200 kHz.If the radio station is changed to AM 600 kHz,by what factor must the capacitance be multiplied to again achieve resonance?

A) 4
B) 2
C) 1/2
D) 1/4

Question 18

An FM radio tuning circuit has a coil with an inductance of 0.0015 mH.What is the value of the capacitance if the set is tuned to 98 MHz?

A) 1.8 × 10−⁶ μF
B) 0.88 × 10−⁶ μF
C) 0.98 × 10−⁶ μF
D) 12 × 10−⁶ μF

Question 19

If the rotating coil used in a generator has its radius doubled,what change results in the amplitude of the voltage produced?

A) It doubles.
B) It quadruples.
C) It is increased by a factor 2^3/2.
D) It stays the same.

Question 20

A 17.0-μF capacitor is connected to an AC source with an rms voltage of 120 V and a frequency of 60.0 Hz.What is the rms current in the capacitor?

A) 1.41 A
B) 0.543 A
C) 0 A
D) 0.769 A

Question 21

An AC series circuit contains a resistor of 20 Ω,an inductor of 50 mH,and a variable capacitor.If the frequency of the applied voltage is 500 Hz,to what setting should the capacitor be set if resonance is achieved?

A) 2.4 µF
B) 3.4 µF
C) 2.0 µF
D) 0.8 µF

Question 22

What is the impedance of an AC series circuit that is constructed of a 10.0-Ω resistor along with 24.0-Ω inductive reactance and 7.0-Ω capacitive reactance?

A) 19.7 Ω
B) 11.2 Ω
C) 41.0 Ω
D) 27.7 Ω

Question 23

Consider an AC series circuit containing a coil,capacitor,and resistor.Doubling the frequency will change the inductive reactance by what factor?

A) 1.0
B) 1.41
C) 1/2
D) 2.0

Question 24

A series LCR circuit has a inductive reactance of 2 Ω and a capacitive reactance of 1/2 Ω.By what factor should the AC frequency be changed to put this circuit into resonance?

A)

B) 4
C)

D) This circuit cannot be made to achieve resonance.

Question 25

Consider an AC series circuit containing a coil,capacitor,and resistor.Doubling the frequency will change the circuit's impedance by what factor?

A) 2.0
B) 1.0
C) 1/2
D) Information is insufficient to determine answer.

Question 26

In an LCR series circuit with X_L > X_C,the phase angle between the current and voltage phasors is 30°.If the AC frequency doubles,what is the magnitude of the resulting phase angle?

A) 30°
B) less than 30°
C) more than 30°
D) Additional information is needed to reach a determination.

Question 27

A 50-Ω resistor,a 0.1-H inductor,and a 20-µF capacitor are connected in series to a 60-Hz source.The rms current in the circuit is 3 A.Find the rms voltage across the resistor,the inductor,and the capacitor.

A) 150 V,113 V,398 V (all rms)
B) 150 V,113 V,796 V (all rms)
C) 0.06 V,80 V,562 V (all rms)
D) 60 V,80 V,398 V (all rms)

Question 28

What is the magnitude of the phase angle of an AC series circuit that is constructed of a 10.0-Ω resistor along with 20.00-Ω inductive reactance and 7.00-Ω capacitive reactance?

A) 18.4°
B) 26.6°
C) 52.4°
D) 59.5°

Question 29

A resistor and capacitor are connected in series with an applied AC voltage source.Separate voltmeter readings across the resistor and capacitor give values of 50 V and 60 V (rms),respectively.What is the effective (rms)voltage of the source?

A) 78 V
B) 90 V
C) 110 V
D) 25 V

Question 30

A series LCR AC circuit is at resonance.It contains a resistor of 16 Ω,a capacitor of 0.35 μF,and an inductor of 90 mH.If an effective (rms)voltage of 150 V is applied,what is the effective (rms)current when the circuit is in resonance?

A) 9.4 A
B) 3.3 A
C) 5.0 A
D) 16.1 A

Question 31

An AC series circuit contains a resistor of 20 Ω,a capacitor of 0.75 μF,and an inductor of 80 mH.What frequency should be used to create a resonance condition in the circuit?

A) 650 Hz
B) 530 Hz
C) 160 Hz
D) 320 Hz

Question 32

A resistor,inductor,and capacitor are connected in series,each with effective (rms)voltage of 65 V,150 V,and 80 V,respectively.What is the value of the effective (rms)voltage of the applied source in the circuit?

A) 295 V
B) 48 V
C) 96 V
D) 88 V

Question 33

Find the resonant frequency for a series LCR circuit where R = 20.0 Ω,C = 10.0 µF,and L = 8.0 mH.

A) 1.59 kHz
B) 563 Hz
C) 5.00 kHz
D) 796 Hz

Question 34

In an RL circuit,which of the following is a possible magnitude of a phase angle?

A) 45^°
B) 315^°
C) 225^°
D) 135^°

Question 35

An AC series circuit has 8.00-Ω resistance,15.00-Ω inductive reactance,and 10.00-Ω capacitive reactance.If an effective (rms)emf of 120 V is applied,what is the effective (rms)current value?

A) 26.0 A
B) 5.31 A
C) 9.23 A
D) 12.7 A

Question 36

In an LCR series circuit the capacitive reactance is 24 Ω.If the AC frequency halves,what will be the resulting capacitive reactance?

A) 24 Ω
B) 48 Ω
C) 12 Ω
D) Additional information is need to find the value.

Question 37

An LCR circuit has resistance R₀,inductance L₀,and capacitance C₀.If the resistance value is now tripled,which values of inductance and capacitance will result in the same resonant frequency as before?

A) 3L₀,C₀
B) L₀/3,C₀/3
C) 3L₀,3C₀
D) 3L₀,C₀/3

Question 38

A resistor,inductor,and capacitor are connected in series,each with an effective (rms)voltage of 65 V,140 V,and 90 V,respectively.What is the magnitude of the phase angle between the current and applied voltage phasors in this circuit?

A) 38°
B) 28°
C) 22°
D) 43°

Question 39

Consider an AC series circuit containing a coil,capacitor,and resistor.Doubling the frequency will change the capacitive reactance by what factor?

A) 1.41
B) 1.0
C) 2.0
D) 1/2

Question 40

In an LCR circuit,the maximum current is 1 amp.What is the average current?

A) (1/2)A
B)
A
C)
A
D) None of these choices.

Question 41

An electric motor produces 2.0 hp in a V_rms = 120 V circuit.What is I_rms for this motor? (1 hp = 746 W)

A) 12 A
B) 6.2 A
C) 0.62 A
D) 1.6 A

Question 42

An AC power generator produces 100 A (rms)at 3600 V.The voltage is stepped up to 100,000 V by an ideal transformer,and the energy transmitted through a long-distance power line with a total resistance of 100 Ω.What is the rms current in the long-distance line?

A) 3.6 A
B) 1.0 A
C) 1000 A
D) 1.8 A

Question 43

A transformer consists of a 1000-turn primary coil and a 4000-turn secondary coil.If the current in the secondary is 3.00 A,what is the primary current?

A) 6.00 A
B) 0.750 A
C) 48.0 A
D) 12.0 A

Question 44

A transformer is to be designed to increase the 30 kV (rms)output of a generator to the transmission line voltage of 345 kV (rms).If the primary winding has 60 turns,how many turns must the secondary have?

A) 57
B) 6900
C) 690
D) 11

Question 45

An AC power generator produces 25 A (rms)at 3600 V.The energy is transmitted through a long-distance power line,which has a total resistance of 50 Ω.What percentage of the power delivered by the generator is dissipated as heat in the long-distance line if a step-up transformer is not used?

A) 69%
B) 35%
C) 0.09%
D) 1.8%

Question 46

The primary winding of an electric train transformer has 200 turns,and the secondary has 50.If the input voltage is 120 V(rms),what is the output voltage?

A) 30 V
B) 15 V
C) 10 V
D) 480 V

Question 47

Transmitting power at high voltage,e.g. ,400,000 V,reduces the power loss for transmission lines.But such a voltage would destroy electrical devices in household use.How then can such 400,000 V electricity be used in a normal house?

A) The ground prongs on household plugs reduce the voltage to 120 V.
B) Before reaching households,transformers are used to reduce the voltage appropriately.
C) No matter the incoming voltage,a 120-V device only lets 120 V in.
D) The 400,000 V is just theoretical;long distance transmission lines actually use 120 V.

Question 48

An electric motor produces 2.0 hp in a V_rms = 120 V circuit.Using 1 hp = 746 W,how long would it take this motor to do 1.0 kWh of work?

A) 0.67 min
B) 0.67 h
C) 1.3 min
D) 1.3 h

Question 49

In an AC circuit operating at a frequency where the phase angle with respect to the current is 30°,what happens to the phase angle if the capacitance of the circuit is increased?

A) It increases.
B) It decreases.
C) nothing
D) It decreases and can become zero.