AC Circuits Questions and Answers

1 A voltage e t 100sin314t is applied to a series circuit consisting of 10 resista 0 0318H inductance and a capacitance of 66 3 F Determine i Expression for i t ii Phase angle between voltage and current iii Power factor iv Active power consumed Also draw the phasor diagram

Tes a A coil with internal resistance takes 2 5A when connected across 200V 50Hz supply The power consumed by the coil is found to be 450W Find the power factor and inductance of the coil

Question 16 If a direct current of value a ampere is superimposed on an alternative current I b sin wt flowing through a wire what is the effective value of the resulting current in the circuit dc a A O Only one option is correct a pas ac 71 2

A square loop containing an inductor of inductance 4 H and a capacitor of 2F is fixed in the plane of wires infinitely long carrying current I 4t Amp and I 2t Amp as shown in th figure where t is the time in seconds after the circuit was setup Choose the CORRECT option s a A B O L 00000 Maximum charge on capacitor is 4 In 2 T 2u a

The maximum energy stored in the inductors is x J The value of x is cha 892 A B 16 V L 23H 2 Your Answer ellee L 36 H

c Design a noninverting amplifier circuit that is capable of providing a voltage gain of 15 Assume ideal op amp and resistance should not exceed 30 KN d Find the output of the following circuit 2

2 0 5 3 0 8 4 1 0 An inductor 20 mH a capacitor 50 F and a resistor 40 are connected in series across a source of emf V 10sin340t The power loss in A C circuit is NEET 2016 1 0 89 W 2 0 51 W 3 0 67 W 4 0 76 W source are all connec removed from the cir between the voltage If instead C phase difference the circuit is 1 1 imited Reads Office Askash Tower 8 Pusa

Mark the incorrect statement 1 In any AC circuit the applied instantaneous voltage equals to the algebraic sum of the instantaneous voltages across the series elements of the circuit 2 For circuits used for transporting electric power a low power factor implies large power loss in transmission 3 Power factor can often be improved by the use of a capacitor of appropriate capacitance in the circuit 4 The use of a capacitor is avoided in the circuit of an induction coil LC Oscillations Transformers intor on 220 V line and

and d 4 a and b 3 a b c d A circuit when connected to an AC source of when connected to a DC source of 12 V gives a current of 0 4 A The circuit is 1 Series LCR 3 Series RC NEET 2019 Odisha 2 Series LR 4 Series LC

52 As shown in figure if capacitor of capacitance C is charged by connecting it with a resistance R then energy given by battery will be fay my fagur af cuka a ya ufadu ma C 1 12 CV 1 CV 2 Less than 2 CV 2 CV 354 www R 3 CV 3 CV GR 4 More than CV 4 CV 3h

A cassette recorder uses a plug in transformer to convert 120 V to 12 V with a maximum current output of 493 mA a What is the current input b What is the power input MA W c Is this amount of power reasonable for a small appliance Select an answer

ectangular coil consists of N 130 closely wrapped turns and has dimensions a 0 400 m and b 0 300 m The coil is hinged along the y axis and its plane makes an angle 30 0 with the x axis figure B X a What is the magnitude of the torque exerted on the coil by a uniform magnetic field B 0 840 T directed in the positive x direction when the current is I 1 20 A in the direction shown N m b If you are looking downward from the positive y direction what is the expected direction of rotation of the coil Oclockwise

In a series RLC circuit the current is observed to lag the e m f by 45 If the inductive reactance is found to be thrice of the resistance R then the capacitance of the circuit will be frequency of applied emf is f 1 2 1 2xfR 3 4xfR 4xfR 4 2nfR

PASSAGE In an ac circuit it is containing resistance of 15 ohm and inductance of 0 3H in series with 50Hz ac supply voltage If the voltage across resistance and inductance is 10 volt and 15 volt respectively Then determine following unkown parameters Choose the correct options Marks Calculate the power factor of the circuit OPTIONS 0 157 0 176

Choose incorrect statements An inductor of inductance L capacitance C and resistance R are connected in series to a variab sinusoidal voltage supply whose frequency is variable but rms voltage is constant At resonance Average power will be maximum III Impedence will be maximum II Average power will be minimum IV current and voltage will be in same phase A I and IV C I and III B II and III D II III and IV

For the given ac circuit source voltage is given by V 77 100 sin 10t 2 where V is in volt and t is in second 1 2 R 10 39 www Question Type Single Correct Type 3 L 1H 000000 ac source Power factor of the given circuit is 2 Current as a function of time t is given by i A 5 sin 10t 2 Voltage across resistor as a function of time 75

The resistance of a coil for dc is R ohms When connected to ac supply the total resistance offered by circuit to ac current A Will remain same B Will increase C Will decrease D Will be zero Correct Answer

PASSAGE Consider a resistance of 2002 an inductance of 0 2 H and a capacitance of 100 F are connected in series across 220 V 50 Hz mains Determine the following Choose the correct option Marks 2 Calculate voltage drop across inductance OPTIONS 384 51 V

At resonance in a series LCR circuit which of the following statements is true 1 Current in the circuit is maximum and phase difference between E and I is 2 2 Current in the circuit is maximum and phase difference between E and I is zero 3 Voltage is maximum and phase difference between E and I is 2 4 Current is minimum and phase difference between E and I is zero

The rms value of an alternating current which when passed through a resistor produces heat three times of that produced by a direct current of 2 A in the same resistor is 1 6 A 2 3 A 3 2 A 4 2 3 A

An ideal choke draws a current of 8 A when connected to an AC supply of 100 V 50 Hz A pure resistor draws a current of 10 A when connected to the same source The ideal choke and the resistor are connected in series and then connected to the AC source of 150 V 40 Hz The current in the circuit becomes 1 15 A 2 3 18 A 2 8 A 4 10 A

A coil has an inductance of joined in series with a resistance of 22092 When an alternating e m f of 220 V at 50 cps is applied to it then the wattless component of the rms current in the circuit is 1 5 ampere 2 0 5 ampere 3 0 7 ampere 4 7 ampere T H and is 35

In a certain circuit current changes with time according to i 2 t r m s value of current between t 2 to t 4s will be 1 3A 2 3 3A 3 2 3 A 4 2 2 A

In the circuit shown in figure the current measured by ammeter is 60V 1 2 1 A R 100 Question Type Single Correct Type 2 A V mmmm 50V 100V HH

with time as 0 X is unknown circuit element then the maximum reading of the voltmeter V is V 20sinwt and V 20 cos Options O 20 2 V O 10 3 V 020 V voltmeters vary X A X cot T 6

An inductor of inductance 20 mH is connected across the terminals of a capacitor of capacitance 2 F which is initially charged to a potential 10 2v The charge on the capacitor when the energy stored in the capacitor becomes equal to the energy stored in the inductor is O 20 C O 10 C O 5 C O 25 C

When 100 V DC is applied across a solenoid a current of 1 A flows in it When 100 V AC is applied across the same coil the current drops to 0 5 A If the frequency of the AC source is 50 Hz the impedance and inductance of the inductor for the given AC circuit are O200 Q and 0 55 henry O 100 Q and 0 86 henry O 100 Q and 1 0 henry 100 Q and 0 93 henry

A Daniel cell is connected to the primary coil of a transformer If the output voltage of the Daniel cell is 10 V and the ratio of secondary to primary coil turns of transformer is 2 then the voltage in the secondary will be 05V O 10 V O 20 V O Zero

80 A 500 H inductor pF capacitor and a 6280 resistor are connected t form a series LCR circuit Calculate the resonant frequency and Q facto of this circuit at resonance O fr 2500 kHz Q 10 O fr 2500 kHz Q 12 5 Ofr 3000 kHz Q 10 O fr 3000 kHz Q 12 5

30 Which of the following has dimensions different from remaining three V E H 7 1 Qlou 117 of Inductance Resistance 2 Resistance x capacitance Inductance x capacitance 1 3 4 C H 1 Inductance 1 capacitance Resistance X i rect I 9 H I

A choke coil is needed to operate an arc lamp at 250 V rms and 50 Hz The lamp has ar effective resistance of 1502 when running at 10 A rms The inductance of the choke coil is N 125T H Find the value of N

In the shown figure B and B2 are two boxes which can contain only R or C or L or series combination of any two or a three If emf of source S and current through source are in phase then mark the correct option S B B If B contain R then B may contain R only IfB contain R then B may contain L C R If B contain L R then B2 may contain R C If B contain L R then B may contain L C R

Please type the answer provided space without unit In a Audio headphones capacitor of capacitance 2 F is connected across the alternating voltage with r m value Vrms of 270 V to improve audio quality If the r m s current Ims in the circuit is 4 5 A Find 1 the Capacitive reactance of the circuit in ohm 1 0 Mark ii the frequency in Hz of the source voltage 1 0 Mario

In the circult shown the power factor of the circuit is 1 power factor of box is 4 5 source voltage is 100V angular K Henry then find frequency 100 rad sec and current flowing in circuit is 5 amp Value of inductance of inductor is 20 value of K A 5 Amp Box 100 V 100 rad sec

What will happen to the current in this circuit as frequency increases 5 V RMS 0 22 F A Current will remain the same B Cannot tell not enough information given C Current will decrease D Current will decrease to a minimum and then increase Se

9 a Determine and sketch the output voltage for the following circuits The diode is made of silicon with forward voltage drop 0 7 V ii 10 V 0 10 V R o W 0 1 0 kn 3 3 V 5 1 V 18 V A 18 V R w 10 kf2 12 V R 100 2 220 0 IN914 UP

In the circtuit shown which of the following statement is are CORRECT 1 2 Question Type Single Correct Type 3 V 100 2 sin 377t 4 R 1000 X 1000 AAAAAA VOTROVO X 5001 1 Power factor of the circuit is 2 Reactance of the circuit is equal to resistance of the circuit Circuit is not in a state of resonance X 1000 Average power dissipated in the circuit is 100 W C

9 In the circuit shown the value of capacitive reactance X if net current is in phase with the applied voltage V is nearly 1 14 Q 102 www 5Q www X 20 2 000 2 34 Xc HI

Draw the No load phasor diagram and equivalent circuit of a practical single phase transformer and highlight all necessary parameters

Aakash Institute 32 A current passing through a hot wire ammeter is made of two components a dc component i 3A and an ac component i 4 2 sin cot Find the reading of the ammeter 1 1A 2 5A

Alternating Current 26 In a dc LR circuit current grows to th of its steady 4 state value in 2 s The time constant of LR circuit is 2 2 1 3 In 3 2 In 2 4 2 In 4 32 33

5 Which of the following statement is incorrect about series resonance circuit 1 We can have resonance in a RL and a RC circuit 2 Resonance in a circuit occurs when L and C both are present in the circuit 3 At resonance voltage across the L and C are 180 out of phase 4 At resonance the total source voltage appears across R

The impedence of a series LCR circuit varies with frequency of applied voltage source as below Z 3z 9 00 Identify the correct option 00 1 At current lags the source emf by radians 2 At current leads the source emf by radians 3 0 0 00 4 All of these Q W 4 pla The graph between charge Q in coulomb and time t in second is parabolic The average current in the interval 0 to 4 second is 2 pr 10 0 1 2 amp 2 1 amp 3 16 amp 4 4 amp The r m s value of current for one teric period in the above diagram which is plotted between i and t is 4 1 2 A Telegram eetquestion paper 1 3 2 2 A The value of C if circuit becomes resonant after closing the key is CL 1 R 3 0000000 V V sinot A 1 4 2 2 A L 00 L 5 A series LCR circuit is in resonance at a frequency 0 0 000 At 00 29 the best phasor diagram K 2 C C representing the relation between current and voltage phasor is JY 4 Vy

3 Zero 4 1 5 Volt 1 The electric current in a circuit is given by i i for some time Calculate the r m s current for the period t 0 to t t 1 m 3 m 1 7 22 2 2 3 12 An inductance L having a resistance Ris 4 23

In an ac circuit V and I are given by V 100 V sin 100 rt and I 100 mA sinh 100rt The power dissipated in the circuit is 1 5000 W 2 5 W 3 2 5 W 4 Zero EN 2

33 In the given LCR series circuit find the source frequency which drives the circuit at resonance 1 25 Hz 3 50 Hz C 80 F L 5H ooooo V 200V N B R 4002 K 50 Hz Hz

5 A transformer is used to light 140 watt 24 volt lamp from 240 volt AC mains the current in the main cable is 0 7 amp The efficiency of the transformer is 240 volt A C An4 140 watt 24 volt a i YchifeTa a i fo l ch i 34 n fre main cable 0 7 amp T 2 84 1 63 8 3 83 3 4 48

The following circuit uses three ideal ammeters showing rms values Then regarding the reading of ammeter A3 C L2 ooooooo 200 V 250 3 L ooooooo Hz C A A3 10 A A A As Correct Answer C 300 F C 400 F L 240 mH L 30 mH

4 0 56C 40 Bulb 1 and Bulb 2 are identical Key is closed at t 0 and after the bulbs start glowing with their full intensities the key is opened Which of the following is correct DOODO 1 www key 1 At t 0 both bulbs glows with equal intensities 2 At t 0 no bulb glows 3 At t 0 only bulb 1 glows 4 After key is opened both bulh glows with

You have a 200 Q resistance a 4 00 H inductor and a 100 0 F capacitor and a variable frequency AC source with an amplitude of 3 00 volts You connect all four elements together to form a series circuit list I various angular frequency of source where as list II various observations related to the circuit match the column 4 00 200 g 100 0 F ka am yg 3 00 y y Raff ya AC za 61 33 AH MR ty jsce yc stuff Ry Affa 1 za a f a fa cufu 11 f a fa fa gu yf t Ama hi List I List II f 11 P Q R w 30 rad s w 50 rad s w 70 rad s S w zero W 2014 A B C D 1 Current in the circuit is greatest 2 Voltage leads the current 3 Current leads the voltage 2 Current fades away after sometime UA HO HAY MGA 14 P 2 Q 1 R 3 S 4 P 3 Q 1 R 2 S 4 Correct Answer P 2 Q 1 R 4 S 3 P 1 Q 3 R 4 S 2