AC Circuits Questions and Answers

Q1 A non inductive resistor is connected in series with a capacitor of 100 F capacitance across 200 V 50 Hz mains The p d measured across the resistor is 150 V Find the value of resistance and the value of current taken from the mains if the resistor were connected in parallel with the capacitor instead of in series

2 In a series RC circuit a resistance and capacitance are connected in series in such a manner it takes 220V ac supply The values of resistance and capacitance are 20ohm and 0 6 microfarad The supply frequency is 50Hz of the circuit Determine total impedance of the circuit 2 MARKS

Which one of the is not features of TDMA Duplexers are required Data transmission is not continuous but occurs in bursts O Shares a single carrier frequency with several users where each users makes u non overlapping time slots Uses different time slots for transmission and reception

A student is working on a project as they require to analyze and compose a circuit in which a coil having inductance of 0 03H and resistance of 60 connected across 200V 50Hz supply 1 Evaluate inductive reactance of the circuit

08 The coils have a mutual inductance of 0 005 H The current changes in the first coil according to equation I I sin oot where I 10 A and 0 0 100 rad s The maximum value of emf in volt in the second coil is a 2 b 5 c d 4

01 In the circuit shown in figure L 10H R 50 E 15 V The switch S is closed at t 0 At t 2s the current in the circuit is L voor a 1 1 A 3 e c 3 A E R S b 1 31 A e d 3 17 A

If in any circuit it consists of basic elements such as resistance inductance and capacitance Then by considering all parameter derive the relation of voltage and current for inductor element

a A series RLC circuit has L 20 mH C 100 nF R 20 2 and Vmax 100 V with v Vmax sin wt Find i the resonant frequency of the circuit ii amplitude of the current at the resonant frequency iii amplitude of the voltage across the inductor at resonance b What maximum current is delivered by an AC source with Vmax 48V and f 90 Hz when connected across a 3 70 mF capacitor 16 maks 12 4

20 The network shown in figure is a part of complete circuit If at a certain instant the current i is 4 A and is increasing at a rate of 103 A s Then VB VA will be Awwww 12 1 11 V 3 21 V moros B 12 V 5 mH 2 11 V 4 21 V

For the below circuit what is the voltage Vy Pick the closest answer love Req 0 91 V V O ov 3KM Im H VX 5kA IMF Vw VW 5 F Circuit is in steady state Vy 50 Kn 10 KA 33mH

19 When an alternating voltage E E sin ot is applied to a circuit a current 1 1 sinot flows through it The average power dissipated in the circuit is a rms EL rms b El d Zero 03

skip Case study LC circuit shown in figure have a capacitor of capacitance C and n inductor of inductance L 412 C 1 Capacitance of capacitor in the circuit is 10 3 10 H Answer the following question f initial current is 2 mA and charge on capacitor is zero then find out current in inductor when charge on capacitor is 2 C tions Zero mm L 1 mA 0 5 mA F and Inductance of inductor is

4 b Two currents in and i2 are given by the expressions i 10 sin 314t 4 amperes and i2 8 sin 313 t 3 amperes Find a i 12 and b i i2 Express the answer in the form i Im sin 314 t q 5

For a series LCR circuit with R 10002 hathong L 0 5mH and C 0 1pF connected across 220 V 50 Hz AC supply the phase angle between current and supplied voltage and the nature of the circuit is 1 0 resistive circuit mathango 2 90 p 3 0 resonance circuit 00 mgthongos mothongs mathongo mothono mothongo mothongo predominantly inductive circuit mothongo mathange mathongo mathongo mathongo mathongo mathonge mothont mathong

9 The transfer ratio of a transistor is 50 The input resistance of the transistor when used in the common emitter configuration is 1 k The peak OP Sp value of the collector A C current for an A C input voltage of 0 01 V peak is 1 0 25 mA 2 0 01 mA 3 100 A

5 An ac source is connected across an element X The variation of voltage E and current I with oot is shown in the figure then the element X is E I Ky T 2 2x 3 2 Eo To cof A Inductor and voltage lags the current by 2 B Capacitor and voltage leads the current by 2 C Capacitor and voltage leads the current by 2 D Inductor and voltage leads the current by 2

n and from the e at 1 The plate e negative charge im at 1 until the q C is in phase e at 1 Current vi is positive THE SOURCE CLE AS THE Charge Discharge 2 Vc 1 2 The current i reverses its direction The accumulated charge is depleted i e the capacitor is discharged during this quarter cycle The voltage gets reduced but is still positive The current is negative Their product the power is negative THE ENERGY ABSORBED DURING THE 1 4 CYCLE 0 1 IS RETURNED DURING THIS QUARTER How this ve Charge Discharge B 3 Lease explain the underline cher can you explain I write the question in photo a

53 In the circuit shown the voltage leads the current by T 4 The resistance R of the circuit is estionpaper L 0 8 H 000000 1 13 5 Q R www V 100 sin 50t Vis in volt and t is in second 2 25 2 2

80 A 500 H inductor pF capacitor and a 628 Q resistor are T connected to form a series LCR circuit Calculate the resonant frequency and Q factor of this circuit at resonance fr 2500 kHz Q 10 fr 2500 kHz Q 12 5 fr 3000 kHz Q 10 fr 3000 kHz Q 12 5

4 In L C R series AC circuit the voltage across each of the components L C and R is 50 V The voltage across the L C combination will be L C R AC ad un all 50 V L C ami 1 50 V 2 50 2 v 3 100 V 4 Zero volt

ALLEN For a logic gate A B are input and C is output 42 voltage waveform then logic gate is 1 OR 3 NOR 2 AND 4 NAND af fefta areal 1 OR 3 NOR fer A a B fraft an c fria at an 2 AND 4 NAND

Resistance R and R are 52 and 5 30 respectively Reactance of inductor is 5 302 andth of capacitor is 502 Source voltage oscillation is V 10 2 sin cot volt The average powerdelivered by source is nearly 2x watt Find x R R w 11

6 An Alternating Current circuit consists of a resistance and an ideal choke coil in series The resistance is of 2200 and choke coil is of 0 7H The power absorbed from 220V and 50Hz source connected with the circuit is 1 55 W 3 110 W 2 2 2 220 W 4 440 W

In an oscillating LC circuit maximum current in inductor is I The current in inductor when the energy is stored equally between the electric and magnetic field is 1 11 12 24 3 lo 2 4 1

2 The peak value of alternating e m f E is given by E E coswt is 20 volt and frequency is 50 Hz The average value of e m f is The average is taken over first half of time period 1 20 2 T 10 volt 2 10x2 T volt

1 An inductor of inductance 10 mH and capacitor of capacitance 5 F are in LC oscillation If maximum energy stored in capacitor is 2J the maximum current in the circuit is 1 0 2A 3 20A 2 2A 4 5A

0 In an AC LCR series R 100 2 When capacitance C is removed the current lags behind T the voltage by When inductance L is removed 3 TC the current leads the voltage by The impedance 3 of the series combination circuit is 1 50 Q 2 100 Q 3 2008 4 400 2

A transformer has Np 30 turns in primary and N 2500 turns in the secondary If the input voltage is V 200Sin wt then the r m s voltage across the secondary coil is approximately 1 1000 volt 2 1100 volt 3 1200 volt 4 11786 9 volt

If current consider the following ac circuit from the source is plotted against frequency of voltage source the graph is best respected by 2 3 Wo R 0

onsider the L R C circuit with L 1 H R 40 C 1 4000 F and t 24 V Determine the current in this circuit if there is zero initial current d zero initial charge A 0 008 0 006 0 004 0 002 0 05 01 0 15 03 0 35 B 1 0 25 0 2 0 15 0 1 0 05 0 05 0 15 Plots of the charge and current in an L R C circuit 0 25 0 35

In a series L C R circuit the values of L and C are so adjusted that the maximum current flows through the circuit In this case if the P D across L is 200V then the P D across the capacitance will be A More then 200 V YOU B Less then 200 V C Equal to 200 V

In an A C circuit a resistance R 400 and an inductance L are connected in series If the phase angle between voltage and current is 45 then the value of the inductive reactance will be YOU A 200 B 40 Q C 100

mateva to sornstala on bsoubor viss In the series LCR circuit as shown in figure the heat developed in 80 seconds and amplitude of wattless current is factor A 4000 J 3A C 4000 J 4A wollol B 8000 J 3A 8000 J 5A LIE R 40 x 70 w 100000 X 40 HH E 25 sin 100xt n 2 orage value of current during tim

Figure shows three oscillating LC circuit with identical inductors and capacitors If t t2 t3 are the time periods of the circuits I II and III then e 1 HH O t 1 t3 O t 1 13 O t t t3 t3 t t ele 11 ele III

Which of the following curves correctly represents the variation of capacitive reactance Xc with frequency f Xc Xc Xc Xc

For an L R circuit in which current is growing the time constant is equal to L RUR Ay MH ug d cst ad chimich A Twice the ratio of energy stored in magnetic field to rate of dissipation of energy in the resistor au aufa Guf au ufadug 7 Guf a ci guai stai Correct Answer B Half the ratio of energy stored in the magnetic field to the rate of dissipation of energy in resistor yachu au a guf au ufauc uf a cu a Ratio of energy stored in inductor at any time to the ratio of energy dissipated in the resistor till that time g zuka kuf auch auf qua audz ata D Ratio of square of the energy stored as magnetic field to the rate of energy dissipated in the resistance a kufa af f u fa

16 1 10 2 N m 3 10 0 N m 2 10 11 N m 4 10 N m A series R L C circuit is shown here The source frequency f is varied but the current is kept unchanged Which of the curves showing changes of Ve and V with frequency would be valid for the circuit under consideration R The magnetic induction at the centre 0 Fig ist 1 1012 N m 2 10 N m 3 1010 N m 4 10 N m 16 fagur R L Caff en fra stafrafferen 17 3 www L C ww en XX

A circuit when connected to an AC source of 12 V gives a current of 0 2 A The same circuit when connected to a DC source of 12 V gives a current of 0 4 A The circuit is a series LR c series LC b series RC d series LCR diela NEET 3010

If in an A C circuit capacitance C is initially decreased by 20 and then increased by 20 then what will be effect on resonance frequency Ans increased by 2

Previous Years Questions A series LCR circuit is connected to an ac voltage source When L is removed from the circuit the phase difference between current and voltage is T 3 If instead C is removed from the circuit the T phase difference is again 3 voltage The power factor of the circuit is 1 0 5 3 1 0 between current and NEET 2020 Phase 1 2 1 0 4 zero

A resistance of 300 22 and an inductance of A henry are connected in series to an ac voltage of 20 volts and 200 Hz frequency The phase angle between the voltage and current is 1 tan 3 tan 144 Im 2 2 tan 4 tan 4 44 16 300 3 volts 200 Hz fawa siku 1 tan 3 tan of Im 3 le 1 T 2 13 4 2 tan 4 tan 314 215 20 ENTD faror f

Figure shows LC circuit with two inductor and two capacitors The current in circuit is given by 1 12 5 sin 2t faat dan LC 1 12 sin 2t L 3H L 2H select correct statement s f f T 12 L 0000 C C 0 2 F TE 200 A C mF 3 B C cannot be determined from given information C Att energy in inductor L is maximum 0000 L 3 GRI TE must be rem

A EMF of Variable Value of Current T Passing through the coil during time I is 1 VOT 2 VOT 4 Coil of inductance L and is connected to V 3 a source Vo 1 at t 0 RMS Vo VOTTE VI L

When a and B rays are subjected to a magnetic field which is perpendicular to the direction of their motion with their same speed The curvature of path of both the particles are 1 equal 2 more for a particles 3 more for particles 4 none 38

15 A bulb connected in series with a solenoid is lit by an AC source If a soft iron core is introduced in the solenoid then 1 Point the bulb will glow brighter the bulb will glow dimmer there will be no effect on the light produced by the bulb bulb may glow more brighter or dimmer 16 The core of a transformer is laminated because 1 Point Oratio of voltage in primary and secondary may be increased energy losses due to eddy currents may be minimised the weight of the transformer may be reduced rusting of the core may be prevented

7 A step down transformer reduces the voltage of a transmission line from 2200 V to 220 V The power delivered by it is 880 W and its efficiency is 88 The input current is 1 Point 4 65 A 0 045 A 0 45 A

the for A C Phase difference Voltage is I when only switch S is and Phase difference shown in figh between current and Closed S in Closed both the Switches L S circuit shown in 6 when only switch Power factor of the circuit when are open is Value of nix C R S

In an LCR series AC circuit voltage across resistance is 2 volt The inductive and capacitive reactances are 100 and 50 respectively The phase difference between voltage across the circuit and current is 30 then pick up the correct statement s Question Type Multiple Correct Type 1 the resistance of resistor is 5 30 2 3 2 A the current in the circuit is 5 3 4 the voltage of AC source is 3 volts

D A 4000 resistor in series with a 0 1H inductor and 0 5 uf capacitor is connected across a 240V ac supply of frequency 50Hz Calculate the impedance of the circuit the current in the circuit the average power supply iv the resonance frequency 11 iii 2 mark 1 mark 2 marks 2 mark

06 The phase difference between current and voltage when the frequency of applied e m f is 00 w is R 2L resonance frequency in a series LCR circuit is 1 3 R N T 2 T 6 2 TC 4 4 Zero