AC Circuits Questions and Answers

For transistor action n Base emitter and collector regions she have similar size and doping concentration b The base region must be very thin and lig dopod c The emitter base junction is forward bia and base collector junction is reverse bies d Both the emitter base junction as well as base collector junction are forward biased Which one of the following pairs of statement correct 1 a and b 3 a and d 2 b and c 4 a and d

CAREER INSTITUTE 35 In the given A C circuit if value of R is changed then 35 f n veuredt ufqu ti a R 10 V 10 V oooooo 10 V Supply 1 Voltage across L remains same 2 Voltage across C remains same 3 Voltage across LC combination remains same 10 V Supply 1 L 2 C 3 LC e f R PCB 7 to

View in English The potential difference V and the current I flowing through an instrument in an ac circuit of frequency t are given by V 5 cos wt volts and 1 2 sin ut amperes whore w 2mt The power dissipated in th instrument is 0 2 3 4 Correct Answer 1 Your Answer 3 Status incorrect Zoro 10W 5 W 2 5 W

When an AC of 200V is applied across a device X a current of 0 5A flows through the circuit and is in phase with the applied voltage When the same source is applied across another device Y the same current flows through the circuit but it leads the applied voltage by 2 i Name the devices X and Y ii Calculate the current flowing in the circuit when same voltage is applied across the series combination of X and Y

In a series LCR circuit the supply voltage is 130 volt The RMS voltage drop across resistor is 50 volt and RMS voltage drop across inductor is 130 volt the RMS voltage drop across capacitor can be 50 volt 100 volt 250 volt L

When frequency of an AC voltage source applied to a LC series circuit is gradually increased from low value the current in the circuit Monotonically increases First increases and then decreases First decreases and then increases Monotonically decreases

A Capacitor of capacitance C 2uF chargd with qo 60 F is connected to the inductor circuit by closing the switch S Inductor circuit is containing an inductor of inductance L 0 3 mH and capacitance C 4 F Find the maximum current through the inductor in the resulting LC circuit C L

Two resistors of resistances R 300 3 ohm and R 200 2 ohm are connected in parallel The equivalent resistance of parallel combination with error is NCERT Pg 37 1 120 1 8 ohm 2 120 1 ohm 3 120 1 6 ohm 4 120 2 0 ohm If percentage error in measurement G 6 67 employ a of mass is the unit gravitation is

In the R C circuit shown below RC E 200sinot volt 300 Correct Answer A The average power dissipated is 300 watt C gkay af guich D 100 2 B The phase difference between the 4 current in the source and source voltage is sta wo au z a accal gey called Your Answer 100 02 10 100 2 Correct Answer The power factor of the circuit is The power factor of the circuit is 10

4 Self inductance and resistance of a coil are 30mH and 20 respectively It is connected to a 300 resistance and a 2V battery in series How much energy will be stored in the coil 2 4 x 10 51

42 In a series resonant LCR circuit the voltage across R is 100 V and R 1 kilo ohm C 2 micro farad The resonant frequency w is 200 rad s 48 i What is the current in the circuit Mark only one oval 0 01 A 0 10 A 1 0 A 10 0 A 49 ii At resonance the voltage across L is Mark only one oval 0 004 V 0 025 V 250 V 40 V 1 point 1 point

7 In the given circuit the voltage across the load is maintained at 12 V The current in the zener diode varies from 0 50 mA What is the maximum wattage of the diode 20 V a 12 W c 0 6 W ww b 6 W d 1 2 W

One end of a long string of linear mass density 8 0 x 10 kg m is connected to an electrically driven tuning fork of frequency 256 Hz The other end passes over a pulley and is tied to a pan containing a mass of 90 kg The pulley end absorbs all the incoming energy so that reflected waves at this end have negligible amplitude At t 0 the left end fork end of the string x 0 has zero transverse displacement y 0 and is moving along positive y direction The amplitude of the wave is 5 0 cm Write down the transverse displacement y as function of x and t that describes the wave on the string An onom

A capacitor of capacitance C has initial charge Qu and connected to inductor L as shown at t 0 switch S is pressed The current through the inductor when energy in the capacitor is three times of the energy of the inductor is 1 Qo 2 LC C s S 2 DOODOO L Qo VLC

A series LCR circuit has a capacitor 6 25 F in series with a resistance R 300 22 and an inductance L The circuit is driven by a voltage V 240 cos 400 t V N P www R L Q HH C If the circuit is in resonance the magnitude of the voltage drop across the R L segment i e drop across the points P and Q is A 500 V B 400 V C 240 V

8 The primary coil of an ideal transformer has 100 turns and secondary coil has 200 turns Then select the correct option 1 Voltage in primary coil is two times than secondary coil 2 The power in primary coil is two times than the secondary coil 3 The current in secondary coil is two times than the primary coil 4 The voltage in secondary coil is two time than the primary coil

The differential equation governing the voltage v of a parallel RLC circuit is given by d v 1 dv V C 0 dt2 R dt L where L 10 x 10 H and C 5 x 10 6 F Determine the value of R so that the general solution of v t contains oscillations of angular frequency equal to 3500 rad s

Consider the A C circuit as shown in the figure and choose CORRECT option s R M S value of potential difference between A and B is VAB R wwwwww L mmmm A VAR will increase on increasing R AB B R www R V V sinot B V will decrease on decreasing R AB C VAB does not depend on non zero value of R D VAR does not depend on non zero value of c AB

In the circuit shown in the figure the switch S is closed at the moment t 0 C www R wwww R At the moment t RC In2 the currents through each of the two resistors were found to be equal say i Select the correct alternative i R i R 210

A source of alternating EMF is connected to a series combination of L C and R The maximum and minimum value of instantaneous power delivered to the LCR circuit are 3P and P and the phase difference between applied EMF and current through circuit is 2 Find the value of n n Correct answer 06 00

5 A capacitor of capacitance 120 F is connected to a battery of emf 6 00 V and internal resistance 1 00 through resistanceless leads 12 0 us after the connections are made what will be a the current in the circuit b the power delivered by the battery c the power dissipated in heat and d the rate at which the energy stored in the capacitor is increasing 20

In a room heater an alternating current given by the expression A cos ot B sin ot produces heat at the same rate as that by a direct current I The direct current is given by the expression A I dc B I dc C ldc A B 2 A B 2 D Idc A B 2 2 A B 490

37 Block diagram of an amplifier is given as Vor 2 2Sin 157t 3 The value of x is 300350 gain Av the X H 1 x issin 157t 3 when it is a CB amplifier with gain 150 TU 2 x is 350 sin 157t 4 3 when it is a CC amplifier with gain 17 t 3 x is 350 sin 157t 3 when it is a CE amplifer with gain 175 4 x is 350 sin 157t 4 3 when it is a CE amplifier with gain 17 TC

Discharge of capacitor C through inductor L is oscillatory with period T The charge on capacitor at t T 2 is A one fourth of maximum charge B 0 C maximum charge D half of maximum charge

4 40 V 4 40 V 44 In AC circuit E 120 2 sin100at and I 10 2 sin 44 AC E 120 2 sin100t1 10 2 100m then the power consumed in the circuit is 2 120 W 4 Zero 1 1200 W 3 2400 W 100 fev 1 1200 W 3 2400 W sitera fes 2 120 W 4

MA 2015 23 A series R C circuit is connected to an alternating voltage source Consider two situations a When capacitor is air filled b When capacitor is mica filled Karnataka CET 2013 Current through resistor is i and voltage across capacitor is V then a i i b V V d Va V b

0 10 points FM modulator with a carrier fo 1 kHz and kf 80x The carrier amplitude A emcy modulated i talending the demodulator block diagram shown in Figure 2 complete mathematical expressions with numerical values of the signals at points b c and d HAMMA Figure FM modulator Envelope detector H Demodulator Figure 2 DC blocking

B C the following options Circuit component across an ac source 200 rad sec 1002 000000 SH IkQ 500 F 500 F rooooo H 3 F www 000000 SH CTANCE CAPACITAN p q r s t Phase difference between current and source voltage 76 TU TU ALI 70 3 None of the above

A stepdown transformer increases input current from 4 A to 24 A in secondary coil If the number of turns in primary is 660 the number of turns in secondary coil consider ideal transformer O 3960 0 110 O 66 Read 33

5 T Consider a series L R circuit in which L H and resistance R 100 2 When the circuit is connected to a c source 220 V 50 Hz Find the current drawn from the source Impedance Z R L R 4 1 1 100 100 100 202 X 2nfL 100 92 Hence Ims Try Yourself In example 5 V mms Z 220 100 2 1 1 2A De ven Resistuce in L K concurs 476 d fu 2

Question 5 Three electric bulbs 40W 60W 100W are designed to work on a 220V mains Which bulb will burn most brightly if they are connected in sereis across 220V mains A 40W B 60W C 100W D All are equally bright

5 Switch is in position 1 for a long time At time t 0 it is shifted to position 2 Find the maximum charge which will accumulate on capacitor E E 1 RALC R LC 3 LC E R 000 2 2 LC P 4 R E LC

Voltage applied to an AC circuit and current flowing in it is given by 200 2 sin wt and V 2 cos wt 77 Then power consumed in the circuit will be Question Type Single Correct Type 1 2 3 4 200 W 400 W 200 2 W None of these

The diagram shows a inductor C and a resistor R connected in series to an AC source V and V are voltmeters and A is an ammeter Consider now the following statements V 0000 R 1 I only 3 I and II only www A I Readings in A and V are always in phase 1 II Reading in V is ahead with reading in V III Readings in A and V are always in phase Which of these statements are is correct 2 II only 4 II and III only

35 180 In an AC circuit resistance R inductance L and capacitor C are connected in series When Lis removed from the circuit the phase difference between voltage and current in the circuit is 3 If only C is removed from the circuit the phase difference is The phase difference between 4 voltage and current in LCR is 96 tan 3 1 tan 3 1

8 An electric bulb has a rated power of 50W at 100V If it is used on an AC source of 200V 50Hz a choke has to be used in series with it This choke should have an inductance of 1 5H 3 1 1H 2 2H 4 1 35H

An uncharged capacitor of capacitance C is connected to a battery of emf a at t 0 through a resistance R the i the maximum rate at which energy is stored in the capacitor is 1 4R 2 2R ii time at which the rate has this maximum value is 1 3CR In 2 CB In 3 R 3 CR In2 4 2 R 4 3CR In2

83 A condenser of capacity C is charged to a potent difference of V The plates of the condenser are the connected to an ideal inductor of inductance LT current through the inductor when the potenti difference across the condenser reduces to Vis 1 a c C V V L C V V b d C V V L c v

If the rms current in a 50 Hz ac circuit is 5 A the value of the current 1 300 seconds after its value becomes zero is a 5 2A 5 b d 4 To cir a b c

MtG Objective NCERT P woltage source 81 An LC circuit contains a 20 mH inductor and 25 F capacitor with an initial charge of 5 mc The total energy stored in the circuit initially is removed from en the voltage b 0 5 J a 51 c 501 d 500 instead Cis difference is 82 A 1 5 F capacitor is charged of

19 What will be the reading of the voltmeter across the resistance and ammeter in the circuit shown in the figure A a 300 V 2 A c 100 V 2 A mom V 100V HH V 100V R 10092 www V 200V 50Hz b 800 V 2 A d 200 V 2 A

c 1 57 4 71 7 85 d 1 57 3 14 4 71 80 An LC circuit contains a 20 mH inductor and a 50 F capacitor with an initial charge of 10 mc The resistance of the circuit is negligible Let the instant at which the circuit which is closed be t 0 At what time the energy stored is completely magnetic a t 0 b t 1 54 ms d t 6 28 ms c t 3 14 ms

4 In an electrical circuit R L C and ac voltage source 81 are all connected in series When L is removed from the circuit the phase difference between the voltage and the current in the circuit is If instead C is 3 removed from the circuit the phase difference is 82 again The power factor of the circuit is TL 3 b a c 1 d 5 A voltage of peak value 283 Y and varying frequency

LC OSCILLATIONS 76 The natural frequency of oscillations in LC circuit is given by a 2n LC b T 2LC c TIC LC 77 A fully charged capacitor C with initial charge Q is d LC

2 2 5 A voltage of peak value 283 V and varying frequency is applied to series LCR combination in which R 302 L 25 mH and C 400 F Then the frequency in Hz of the source at which maximum power is dissipated in the above is a 51 5 b 50 7 c 51 1 d 50 3

79 An LC circuit contains a 40 mH inductor and a 25 F capacitor The resistance of the circuit is negligible The time is measured from the instant the circuit is closed The energy stored in the circuit is completely magnetic at times in milliseconds a 0 3 14 6 28 c 1 57 4 71 7 85 b 0 1 57 4 71 d 1 57 3 14 4 71

17 Choose the wrong statement wL a The dimensions of are same as that of strain R b The dimensions of 1 LC are same as that of angular velocity c The dimension of LCR are same as that of time d None of the above

57 Figure shows a series LCR circuit connected to a variable frequency 230 V source 80 pF SH oooo The source frequency resonance is a 4 Hz b 5 Hz 40 2 ww which drives the circuit in c 6 Hz d 8 Hz

15 The electric current in a circuit is given by i 3t Here tis in second and iin ampere The rms curren for the period t 0 to t 1s is a 3 A c 3 A b 9 A d 3 A

When an ac source of voltage V V sin1001 is connected across a circuit the phase difference between the voltage V and current I in the circuit is observed to be 4 as shown in figure If the circuit consists possibly only of RC or RL or LC in series find possible values of two elements a R 1 k2 C 10 F 3 b R 1 k2 C 1 F c R 1 k2 L 10 mH d R 10 k2 L 10 mH KA and V r s