Alternating Current Questions and Answers

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Alternating Current Questions and Answers

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Why is alternating current used in homes?
Is AC better than DC?
What does AC stand for in electricity?
How does alternating current work?
What is an example of luminescent light?
How large an inductance, in H, should be connected in series with a 220-volt, 50-watt light bulb if it is to operate normally when the combination is connected across a 110-volt, 60-Hz line? Ignore...
Part a of the drawing shows a resistor and a charged capacitor wired in series. When the switch is closed, the capacitor discharges as charge moves from one plate to the other. Part b shows the amo...
Power is to be transmitted along a taut string by means of transverse harmonic waves. The wave speed is 9 m/s and the linear mass density of the string is 0.009 kg/m. The power source oscillates wi...
The generator in an AC resistor circuit creates a maximum potential difference across the 175 ohms resistor of 243 V. What is the amplitude of the alternating current if the frequency of the genera...
The generator in an AC resistor circuit creates a maximum potential difference across the 175 Ω resistor of 243 V. What is the amplitude of the alternating current if the frequency of the gen...
What is the frequency of the alternating current provided in Canada?
What does it mean to say that a certain current is 60 Hz?
Why are all cores that are exposed to AC flux variations laminated?
The 2014 Tesla Roadster, an all-electric car, has a top speed of 125 miles per hour. Calculate this speed in centimeters per second.
An inductor has a 48.0 \Omega reactance at 60.0 Hz. What will be the maximum current if this inductor is connected to a 50.0 Hz source that produces a 90 V rms voltage?
How to convert DC power to AC power with a formula
Who invented the electric fan?
Consider the following formula of Resistive impedance: Z_R = R. What does it represent and when is it used?
Explain about AC Generator very cleary.
The maximum voltage V_o supplied by the generator in an ac circuit can be represented by a rotating phasor (see the drawing). The value of the instantaneous voltage V at a time t is given by ------...
Why are two-pronged plugs polarized so that they go into outlets only one way?
What is alternating current? What does the alternating current do?
A 108 ohm resistor, a 0.200 microF capacitor, and a 5.42 mH inductor are connected in series to a generator whose voltage is 26.0 V. The current in the circuit is 0.141 A. Because of the shape of t...
What is principal advantage of AC over DC?
The batteries in a portable CD player are recharged by a unit that plugs into a wall socket. Inside the unit is a step-down transformer with a turns ratio of 1:16. The wall socket provides 130 V. W...
Name and state the principle of a simple AC generator. What is its use?
Explain why power lines outside of cities are run at high voltage in terms of voltages, currents, resistance, power transmission and/or power loss. Explain in 100 words or less.
An AC source operating at 60. Hz with a maximum voltage of 170 V is connected in series with a resistor (R = 1.2 k\Omega) and an inductor (L = 2.8 H). (a) What is the maximum value of the current i...
Choose the best answer to the following: The difference between D.C and A.C in electrical circuits is that in D.C, charges flow (a) steadily in one direction. (b) in one direction. (c) to and fro....
State one advantage of using an ac over the dc?
In the US, a typical wall electrical outlet is said to provide 120 volts AC. In this scenario, 120 volts refers to: A. Half of the outlet's peak voltage B. The root mean square of the outlet's pote...
The voltage E in volts in a circuit after t seconds (t>70) is given by E=12 sin(120pi times t). After how many seconds does the voltage first reach 6 volts?
Explain the advantages of the fuel cell technology.
When AC current flows in a circuit, energy is moved into the circuit during the positive half cycle and moved out of the circuit during the negative half cycle. True False Explain.
Accounting is an information system that identifies, records, and communicates the economic events of an organization to interested users. Categorize the following accounting task: selecting econom...
A charged capacitor and an inductor are connected at time t = 0. In terms of the period T of the resulting oscillations, what is the first time at which the following reach a maximum? (a) U_B (b) T...
Alternating current can not be measured by D.C. ammeter because (a) average value of current for the complete cycle is zero. (b) A.C. changes direction. (c) A.C. can not pass through D.C ammeter....
What is the difference between Alternating current and Direct current?
Define the AC and DC currents?
The resonant frequency of an LC circuit is f_0. (a) If the inductance is increased by a factor of four, what is the new resonant frequency? (Use the following as necessary: f_0.) (b) How should the...
The maximum current in an AC circuit is 3.0 A. What is the rms value of the current in the AC circuit?
How are alternating and direct current different?
A hospital emergency room AC generator operates at a frequency of 60 Hz. If the output voltage is at a maximum value (magnitude) at t = 0, when is it next (a) a maximum (magnitude), (b) zero, and (...
Suggest one reason for the fact that the maxima of the output current and output voltage do not occur at the same point in time for AC circuits.
Which of the following statements is true? (a) DC is more efficient than AC. (b) AC is less expensive than DC. (c) Motors only use AC while generators only use DC. (d) Motors and generators can be...
A 1.5 - k\Omega resistor is connected to an AC voltage source with an rms voltage of 120 V. (a) What is the maximum voltage across the resistor? (b) What is the maximum current through the resis...
A 25 \Omega resistance is connected in series with a 30 mH inductance and a 12 \rm{\mu F} capacitor and are connected to a 90-V (RMS) AC. If the frequency of the AC source is 500 Hz, calculate: (i)...
A certain circuit breaker trips when the rms current is 18.5 A. What is the corresponding peak current?
An oscillating voltage of fixed amplitude is applied across a circuit element. If the frequency of this voltage is increased, what will be the effect on current amplitude in each of the following c...
The voltage signal from a standard European wall socket can be described by the equation V(t)=325\sin 100 \pi x , where t is time, in seconds and V is the voltage at time, t. Determine the period f...
A circuit contains only a 48.2 ohm resistor. An AC voltage of peak value 332 V and frequency 58.8 Hz is applied to this circuit. What is the rms current? Answer in units of A.
An 80.0 Hz generator with an rms voltage of 150 V is connected in series to a 3.20 k ohm resistor and a 3.50 microfarad capacitor. Find the phase angle between the current and the voltage.
An AC current is given by I=480 \sin(9.63t),with I in milli amperes and t in milliseconds. Find rms current and the frequency in Hz?
A television station broadcasts at a frequency of 86 MHz. The circuit contains an inductor with an inductance L = 1.2 \times 10 ^{-6} H and a variable-capacitance C. Determine the value of C that a...
A capacitance C and an inductance L are operated at the same angular frequency. a. At what angular frequency will they have the same reactance? b. If L=5.00 mH and C=3.50 u F, what is the numer...
AC voltage V(t) has an rms value of 220 V. What is the peak value of this voltage?
what is the peak voltage corresponding to 120 V rms?
An alternating current E(t) = 120 sin{(121)} has been running through a simple circuit for a long time. The circuit has an inductance of L = 0.41 H, a resistor of R = 8 ohms and a capacitor of cap...
A 21.0 nF capacitor is connected across an AC generator that produces a peak voltage of 5.10 V. Part A At what frequency f is the peak current 51.0 mA ? Part B What is the instantaneous value of th...
Calculate the peak voltage of a generator that rotates its 200 turn, 0.100 m diameter coil at 3600 rpm in a 0.800 T field.
Which of the following is not an advantage of using AC? A) lower power loss than DC B) easy to convert to any voltage C) tastes great and is less filling
A 2700 W arc welder is connected to a 660 V_{rms} ac line. \\ A. Calculate the peak voltage. B. Calculate the peak current.
A transformer has N1 primary turns and N2 secondary turns. The primary coil is connected to an AC source with voltage amplitude V. The secondary coil is connected to a resistor with resistance R. L...
A source delivers an AC voltage of the form \Deltav = 95.4 sin (60\pi t), where \Deltav is in volts and t is in seconds, to a capacitor. The maximum current in the circuit is 0.460 A. (a) Find the...
The current in an AC power line changes direction 60 times every second and its average value is zero. Explain how is it possible for power to be transmitted in such a system. It appears as if what...
Which of the following is not an advantage of AC circuits? a. They have the ability to transmit electricity over larger distances, with fewer energy losses. b. They have cheaper and simpler gener...
A circuit contains only a(n) 0.234 H inductor. An AC voltage of peak value 161 V and frequency 57.9 Hz is applied to the circuit. When the voltage is 162 V, what is AC current? Answer in units of A.
You are riding in a train, gazing into the distance through its window. As close objects streak by, you notice that the nearby fluorescent lights make dashed streaks. Explain.
(Graph) (a) What is the emf frequency f? (b) What is the value of the resistance R? (c) Draw the resistor's voltage and current phasors t = 15 ms.
In an alternating current circuit, voltage can be modeled by a sin function. For a particular circuit, maximum voltage is 100 volts above the midline, and the frequency is 40 cycles per second. Wri...
Find the rms current through a person if she touches a 120 V AC source for the following conditions: A) Standing on a rubber mat which offers a total resistance of 315 k \Omega in mA. B)Standing...
When an AC source is connected across a 22.0 ohms resistor, the output voltage is given by delta v = (220 V)sin(80 pi t). Determine the following quantities. (a) maximum voltage, (b) rms voltage (...
An AC source with deltaVmax = 135 V and f = 40.0 Hz is connected between points a and d in the figure below. Calculate the maximum voltages between points b and d.
The voltage across and the current through a single circuit element connected to an ac generator are shown in the graph. a. At what frequency do charges oscillate in this circuit? b. Determine the...
Do AC ammeters and voltmeters read maximum, root mean square or average values?
Halogen bulbs have some differences from standard incandescent lightbulbs. They are generally smaller, the filament runs at a higher temperature, and they have a quartz (rather than glass) envelope...
A capacitor is connected across an ac generator whose frequency is 745 Hz and whose peak output voltage is 140 V. The rms current in the circuit is 3.0 A. (a) What is the capacitance of the capacit...
Suppose a current is given by the equation I = 1.30\ sin\ 190t, where I is in amperes and t is in seconds. a) What is the frequency? b) What is the rms value of the current? c) If this is the curr...
Suppose a current is given by the equation I=1.60\sin(230t), where I is in amperes and tin seconds. a. What is the Frequency? b. What is the rms value of the current? c. Suppose that this is the...
The current through a 50 Omega resistor is I = (0.80 A) sin(240 t), where t is measured in seconds. What is the rms current? 1) 0.57 A 2) 1.1 A 3) 0.80 A 4) 1.6 A
Suppose the current through a 24.0 \Omega resistor is I = 1.80sin(210t) where I is in amperes and t is in seconds. a) Determine the frequency of the current. b) What is the rms value of the curren...
Suppose a current is given by the equation I = 2.00 sin(250t), where I is in amperes and t in seconds. (a) What is the frequency? (b) What is the rms value of the current? (c) If this is the curren...
An AC adaptor for a telephone answering unit uses a transformer to reduce the line voltage of 143 V (rms) to a voltage 7.7 V. The rms current delivered to a answering system is 433 mA. Part 1) If...
Why should a ticker timer connect to an alternate current and not a direct current?
The figure given below shows a graph of an ac voltage source output. (a) What is the maximum voltage
Debate both sides of the argument for the following statement: "AC is better to use when compared with DC for household electricity."
Household electricity is all AC. Early on Thomas Edison pushed for houses to use DC. Why did AC win out in the end? What do you suppose was Edison's motivation for preferring DC?
A 525-Ohm resistor and a 275-mH inductor are connected in series with an ac generator with an rms voltage of 22.0 V and a frequency of 65.0 Hz. What is the rms current in this circuit?
The drive train of a bicycle has wheels 67.3 cm in diameter and pedal cranks 17.5 cm long. The cyclist pedals at a steady angular rate of 72.0 rev/min. The chain engages with a front sprocket 15.2...
High-intensity desk lamps are rated at 30 W but require only 13 V. They contain a transformer that converts 125 V household voltage. What is the current in the secondary when the lamp is on?
The voltage across a 74 H inductor is described by the equation VL = (25 V)cos(60 t), where t is in seconds. What is the voltage across the inductor at t = 0.50 s?
In a model AC generator, a 495 turn rectangular coil 6.0 cm by 30 cm rotates at 125 rev/min in a uniform magnetic field of 0.56 T. a) What is the maximum emf induced in the coil? (Answer in V) b)...
An AC current is given by I = 495 sin (9.63 t), with I in milliamperes and t in milliseconds. (a) Find the rms current. (b) Find the frequency in Hz.
An AC current is given by I = 475 sin(9.63t), with I in milliamperes and t in milliseconds. (a) Find the rms current. (b) Find the frequency.
Why electricity is transported at high voltages? Knowing P = I 2 R .
An AC generator consists of eight turns of wire, each of area 0 .0722 m^2, and total resistance of 12 \Omega. The loop rotates in the external magnetic field of strength 0.76 T at a constant freque...
In an RLC series circuit, the phase angle between the current and voltage is 30^{\circ}. If the AC frequency doubles, what is the resulting phase angle? a. 30^{\circ} b. more than 30^{\circ} c. le...
A series AC circuit contains a resistor, an inductor of 240 mH, a capacitor of 5.40 micro F, and a source with delta V_{max} = 240 V operating at 50.0 Hz. The maximum current in the circuit is 140...
Before working on a power transmission line, linemen will touch the line with the back of the hand as a final check that the voltage is zero. Why the back of the hand?
An RL series circuit consists of a 50.0 ohm resistor, a 0.500-H inductor, and an AC voltage source operating at a peak (not rms) voltage of 120.0 V. The frequency of the AC voltage source is 60.0 H...
3. Which of the following reactions should have the larger emf under standard conditions? Why? CuSO4(aq) + Pb(s)< --> PbSO4(s) + Cu(s) Cu(NO3)2(aq) + Pb(s)< --> Pb(NO3)2(aq) + Cu(s)
1. Who is Nikola Tesla and why is he popular in Rocky Point? 2. How did he alleviate Mark Twain's digestive problems?
An AC current is given by I = 480 sin( 9.43 t), with I in milliamperes and t in milliseconds. Find the frequency in Hz.
Explain why the transformers are important in transporting electricity through very long distances.
What role do indicators, capacitor, and resistors play in AC circuits?
The coil of a generator has 50 loops of the cross-sectional area of 0.25 \; m^2. What is the maximum emf generated by this generator if it is spinning with an angular velocity of 4.0 rad/s in a 2.0...
Suppose a current is given by the equation I=1.80\sin250t, where I is in amperes and t in seconds. If this is the current through a 45.0 \ \Omega resistor, write the equation that describes the vo...
A particular circuit has a resistance of 20 ohms. If 120 volts are flowing through the circuit, how many watts are consumed? a. 20 watts b. 60 watts c. 120 watts d. 720 watts e. 2,400 watts
The current in a resistor is given by I = (7.2 A) sin(60 \pi t) when a voltage given by V = (240 V) sin(60 pi t) is applied to it. 1. What is the resistance value? 2. What is the frequency of the v...
The voltage supplied to an ac circuit is given by v = 120 sin(377t). What is the voltage at t = 3 x 10^-3 s?
An AC generator has emf E = E_m sin(w_{dt} - pi/4), where E_m = 36.9 V and w_d = 313 rad/s. The current produced in a connected circuit is i(t) = I sin(w_{dt} - 3pi/4), where I = 468 mA. 1) At wha...
In the AC circuit shown in the figure below, R = 70.0 Ohms and the output voltage of the AC source is (Delta)Vmax sin (omega)t. (a) If (Delta)vR = 0.230 (Delta)Vmax for the first time at t = 0.0115...
The primary coil of a transformer has 941,137 loops. The secondary coil has 2,832 loops. The primary coil has a 9 A current and 64 V. Is this a step-up or step-down transformer? Why? Choose one of...
The primary coil of a transformer has 221,792 loops. The secondary coil has 1,812 loops. The primary coil has a 78 A current and 54V. \\ 1.) Is this a step-up or step-down transformer? How do you...
Find the current in an RC circuit if R = 100 ohms, C= 0.01 farad, initial charge = 0, and E = 60 volts.
Where is the input A.C. signal given?
An ac generator consisting of a coil with N turns rotating at angular speed "w" in an external magnetic field B produces a maximum emf E_0. If you now decrease the number of turns in the coil to N/...
A 60 Hz transformer at a large American industrial plant has 69,000 volts and 1 amp flowing through the primary winding into it from TVA. The secondary of this transformer is supplying 480 volts an...
A current that is sinusoidal with respect to time is referred to as \\ A. a direct current. \\ B. an alternating current.
A capacitor is connected across the terminals of a 110 V rms, 60.0 Hz generator. For what capacitance is the rms current 2.8 mA?
True or false. Explain why. When capacitors and inductances are introduced into a DC circuit, we get an AC circuit.
Which reactance will increase when the angular frequency in the circuit increases? A) both capacitive and resistive B) both capacitive and inductive C) inductive D) resistive E) capacitive
What determines the frequency of ac produced in a generator?
A high-voltage transmission line with a resistance of 0.295 ohm/ km carries a current of 1.20 kA. The line is at a potential of 800 kV at the power station and carries the current to a city located...
A sinusoidal voltage has a maximum amplitude of 12 volts and a period of 17 ms. At t = 0, its value is 8.4 volts and is rising. Write an expression for this voltage as a function of time.
A 210 ohm resistor is connected to an AC source with varepsilon_0 = 9.0 V. (a) What is the peak current through the resistor if the emf frequency is 100 Hz? (b) What is the peak current through t...
A 90% efficient transformer has 500 primary turns and 10 secondary turns. If Vp is 120 V (rms) and the secondary now has a resistive load of 15 Ohms, what is the current in the primary?
Why do voltage, current, and power go through zero 120 times per second for 60-Hz AC electricity?
A transformer is to be used to provide power for a computer disk drive that needs 5.4 V (rms) instead of the 120 V (rms) from the wall outlet. The number of turns in the primary is 395, and it deli...
An electric current, I, in amps, is given by I = cos(wt) + sin(wt), where w, not equal to 0, is a constant. What are the maximum and minimum values of I?
What is a commutator used for?
Why is AC current a vector quantity but DC current is a scalar quantity?
An AC generator produces a sinusoidal voltage at 60 Hz with a maximum of 120V. a. What is the average voltage? b. What is the rms voltage? c. If it were a DC generator with the same maximum of 1...
What did Nikola Tesla discover?
What type of current is used in an UPS?
You are mowing your grass with an AC powered electric lawn mower. As you move to taller grass, the lawn mower blade slows down. What happens to the current and voltage going to the lawn mower when...
How are AC currents produced?
How old was Nikola Tesla when he died?
Who was Nikola Tesla? What did he invent and how his inventions influenced the world today?
A light bulb is connected to an unusual 120. Vrms wall socket. The current in the bulb depends on time t according to the relation I(t) = (0.533 A)sin[(328 rad/s)t]. Note that this is NOT a typica...
When did Nikola Tesla live?
When did Nikola Tesla invent electricity?
How many inventions did Nikola Tesla make?
At what two times in the first period following t = 0 does the instantaneous voltage in 81 Hertz Alternating Current equal V_{rms}
What is the Fourier transform of a dc voltage?
Why is A.C. voltage preferred over D.C?
A step-up transformer is designed to have an output voltage of 2200 V (rms) when the primary is connected across a 110 V (rms) source. a. If the primary winding has 86 turns, how many turns are req...
What are some of the advantages of alternating current?
Suppose the emf generated by a coil rotating in a magnetic field is zero at t = 0 and increases to its first peak at t0 = 0.105 ms. Part (a) What is the angular velocity of the coil in rad/s? Part...
If the emf of a coil rotating in a magnetic field is zero at t = 0, and increases to its first peak at t = 0.100 ms. Requirements: (a) What is the angular velocity of the coil? (b) At what time...
Find the time required for a 50 Hz alternating current to change its value from zero to the RMS value.
Why can't you weld aluminum with dc?
True or false? The cables used to transfer electric energy from the generating station to the consumers must be of low resistance to reduce losses due to Joule heating.
The rms current in a 41-Omega resistor is 0.69 A. What is the peak value of the voltage across this resistor?
An AC voltage source is connected to a resistor R = 1.90 times 10^2 ohm. The output from an AC voltage source is given by the expression V = (3.00 times 10^2 V) sin 2 pi ft. (a) What is the rms vol...
An ac voltage whose peak is 180 V, is across a 3100 ohm resistor. (a) What are the rms and peak currents?
In the circuit in the figure above a generator supplies a voltage of E(t) = 50 sin (10 t) V, the inductance is L = 2 H, the resistance is R = 30 ohm, and I(0) = 2. Find the current after t seconds....
An alternating current is supplied to an electronic component with a warning that the voltage across it should never exceed 12 V. What is the highest RMS voltage that can be supplied to this compon...
The maximum current in a 22 mu F capacitor connected to an ac generator with a frequency of 120 Hz is 0.15 A. What is the maximum voltage of the generator? 1) What is the voltage across the capacit...
Calculate the average rate of energy dissipation in the following circuit. A 51.0 mH inductor is connected as in the figure below to an ac generator with E_m= 26.5 V.
A generator uses a coil that has 260 turns and a 0.65 T magnetic field. The frequency of this generator is 60.0 Hz, and its emf has an rms value of 120 V. Assuming that each turn of the coil is a s...
Which of the following is a disadvantage of the use of current liabilities to finance assets? A. Less Flexible B. The Hedging principle C. Higher interest costs D. Greater risk of liquidity
Using the picture of the signal of voltage versus time from the screen of the oscilloscope and assuming that the settings on the oscilloscope are 2 V/div and 2 ms/div, calculate the following: a) A...
A 8.00-nanofarad capacitor is charged up to 14.0 V, then disconnected from the power supply and connected in series through a coil. The period of oscillation of the circuit is then measured to be 8...
In the AC circuit shown in the figure below, R = 70.0 ohm and the output voltage of the AC source is ?Vmax sin(wt). a.) If ?VR = 0.255 ?Vmax for the first time at t = 0.0120 s, what is the angular...
(a) What is the maximum current in a 6.40 micro F capacitor when it is connected across a North American electrical outlet having delta V_{rms} = 120 V and f = 60.0 Hz? (b) What is the maximum curr...
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