AC Circuits Questions and Answers

If the current in the primary coil is reduced from 3 A to zero in 10 second then the induced e m f in the secondary is 15 x 103 volt The mutual inductance of the coil will be A C 10 H 2 5 H B D 0 05 H 10 mH

An LC circuit consists of a capacitor and a coil with a large number of turns Suppose all the lim dimensions of all elements of the circuit are increased by a factor of 2 while keeping the number of tu on the coil constant How much does the resonant frequency of the circuit change A becomes two times B becomes half C becomes one fourth D becomes four times

155 In the LCR circuit shown below if the reading of the voltmeters V and V are same then moo L 1 0 C LC HH C V www 1092 0 V 50 2 sin ost 2 Reading of the voltmeter V is 50 V 3 Reading of the ammeter A is 5 A 4 All of these A

An alternating voltage is applied across a pure inductor then current O lead the applied voltage by an angle 90 degree 1 point lags behind the applied voltage by an angle depend on the value of inductance O remain in same phase with applied voltage lags behind the applied voltage by an angle 90 degree

D In an a c circuit the instantaneous values of e m f and current are E 200 sin 314t volt and i sin 314t 3 A The average power consumed in watts is 1 100 3 50 2 200 4 25

When 100 volt d c is applied across a solenoid a current of 1 0 A flows in it When 100 volt a c is applied across the same coil the current drops to 0 5 A If the frequency of a c source is 50 Hz the impedance and inductance of the solenoid is 1 200 2 and 0 55 H 2 100 2 and 0 86 H 4 100 2 and 0 93 H 3 200 2 and 1 0 H

In the shown AC circuit potential drop across resistance capacito and inductor is mentioned as V Vo V Vc X 40 R 40 www V 25 sin ot Volt Choose the correct option VR 20 sin wt 37 V Vc 20 sin wt 53 V V 5 sin wt 127 V mo X 192 1 5 sin t 37 V

In order to change the range of a galvanometer of GQ resistance from V volts to nV volts what will be the value of resistance in 2 connected in series with it 1 n 1 G 3 nG 2 4 G 1

The voltage V in an alternating circuit obeys the equation V 120 sin 120nt t 0 where t is the time measured in seconds Hint 180 lue of 1 2 Taj b What is the period of the function V In other words How much time needed to get one period of the sine graph

Design the circuit that is determine the values of R and R so that the transistor operates at I 0 4 mA and V 0 5 V The NMOS transistor has V 0 7 V C 100 A V L 1 m and W 32 m Neglect the channel length modulation effect i e assume that 0 10 51 pm

Q16 Two inductor coils with inductance 10 mH and 20 mH are connected in series What is the resultant inductance of the combination of the two coils 20 3 mH 20 mH 30 mH O 10 mH Clear selection

moor 230 V e circuit shown in the figure alongside shows a series LCR circuit L 5 H C 80 F R 2 connected to a variable frequency source of 230 V i Obtain the impedance of the circuit the resonating frequency ii Determine the source frequency which drives the circuit in onance ii Why can t the voltages across R L and C be added algebraically Pointel

38 T What is the coefficient of mutual inductance when the magnetic flux changes by 2 x 10 Wb and change in current is 0 01A 1 2 henry 3 1 2 henry 2 3 henry 4 Zero 38 I ich 404 2 x 10 Wb faf a un fa 0 01A 1 20 3 1 2 2 3 4

37 3 3m A thin circular wire carrying a current I has a magnetic moment M The shape of the wire is changed to a square and it carries the same current It will have a magnetic moment 1 M 3 4 T M 2 J M 37 3 3m ell 1 M 3 M TC a Ft a plate feel s at sa gue gracia sigut M 4 M 4

In an ac circuit shown in a figure B is a box containing some unknown circuit element Box B has a power factor of 1 while overall circuit has power factor of 1 If the supply frequency is 50 Hz then impedance of the box is A B 100 B Zero C

For the circuit shown in figure the rms value of voltages across R and coil are E and E2 respectively The thermal power dissipated in coil is A B C R www E E 2R e E sin cot erms E E E E 2R E 2R L r eeeeee

A series AC circuit containing an inductor 20 mH a capacitor 120 F and a resistor 602 is driven by an AC source of 24 V 50 Hz The energy dissipated in the circuit in 60 s is A 3 39 10 J B 2 26 10 J C 5 65 10 J

A resistor R capacitor of capacitance C and inductor of inductance L are connected in parallel to AC power ot source of voltage sin The maximum current through the resistance is half of the maximum current through the power source Then value of R is A 3 C B 3 1 OL 11 01 OL 1

As shown in the figure ammeter reading is 3 amp and power factor of circuit is The power factor of the box is k 5 Find the value of k V 90 volt w 25 rad sec Box V volt o rad C 1 mF

C L In the above circuit C F R 2002 C R 2 R 1 3 L 10 Hand R 100 Current in L R path is 1 and in C R path it is 12 The voltage of A C source is given by A 60 B www V 200 2 sin 100t volts The phase difference between 1 and 12 is 150

relation between output v input v voltage are best given by you have to answer for very high frequency of input ac source R voooooo B mmmm L A v V 12 Vo 2 in phase R ooooooo Vo V Vo leads v by 4 C C mooooo

Find the average power consumed In Watt in the circuit if a voltage v S 200 2 sin ot is applied to an AC circuit and the current in the circuit is found to be l 2 sin wot 4 SURMIT

Figure shows as parallel LCR circuit connected to a 200V AC source L 5 H C 80 UF and R 40W At resonance let 1 12 and 13 be the rms currents through L C and R Then A 13 and 1 2 11 0 1 B 11 C 12 and 1 13 D 1 12 and 13 0

An alternating voltage v t 220 sin 100nt volt is applied to a purely resistive load of 50 2 The time taken for the current to rise from half of the peak value to the peak value is A B C D 2 2 ms 5 ms 3 3 ms 7 2 ms

In a RLC circuit capacitance is changed from C to 2C For the resonant frequency to remain unchanged the inductance should be changed from L to 1 4 L L 2 2L

Choose the correct statement a the capacitor can conduct in a d c circuit but not an inductor b in d c circuit the inductor can conduct but not a capacitor c in d c circuit both the inductor and capacitor cannot conduct d the inductor has infinite resistance in a d c circuit

in the graph The rms value of voltage is voltage V with time t is shown V Vo 1 2 3 05 N 65 60 5 to 2 to 3 to

This section O P In an a c circuit the voltage applied is E Eosinot The resulting current in the circuit is coset The average power P consumption in the circuit is given b OP 2Edo Edo 2 questions OP zero Of

This section contains 20 SINGLE CORRECT TYPE questions Each question has 4 choices 1 2 3 a When resonance is produced in a series LCR circuit then which of the following is not correct O Current in the circuit is in phase with the applied voltage O Inductive and capacitive reactance are equal O If R is reduced the voltage across capacitor will increase Impedance of the circuit is maximum

tal signals i do not provide a continuous set of values ii represent values as discrete steps iii can utilize binary system and iv can utilize decimal as well as binary systems Which of the above statements are true a i iii only b ii iii only c i ii iii but not iv d all of i ii iii iv

In series L C R circuit voltage drop across resistance is 8 V across inductor is 6 V and across capacitor is 12 V Then 1 Voltage of the source will be leading with current in the circuit 2 Voltage drop across each element will be less than the applied voltage 3 Power factor of the circuit will be 3 4 4 None of the above

A 50 Q resistor is connected in series with a coil and a sinusoidal ac source of effective voltage 50 V If the effective voltage drop across the resistor is 20 V and across the coil is 40 V Find the power developed in coil in watt

For an series RLC circuit the voltage of the circuit is given by Av 120V sin wt and R 2000 L 0 5H C 8uF Find the potential difference between the ends of the inductor in case of resonance condition Se ti iniz cevab n i aretlendi ini g rene kadar bekleyiniz 6 00 Puan A 200 V

In the circuit shown source may be AC or DC At t 0 switch S is closed Choose the correct statement s LLC A B e D After a long time charge on the capacitor will be zero if source is DC After a long time charge on the capacitor will be zero if source is AC After a long time charge on the capacitor will not be constant if source is DC After a long time charge on the capacitor will not be constant if source is AC oooooo S s

Q3 When a pure resistance R pure inductor L and an ideal capacitor of capacitance C is connected in series to a source of alternating emf then current at any instant through the three elements has the same amplitude and is represented as I Iosinwt However voltage across each element has a different phase relationship with the current as shown in graph 0 A resistor of 1202 a capacitor of reactance 1492 and a pure inductor of inductance 0 1H are joined in series and placed across 200 V 50 Hz a c supply i The value of inductive reactance is a 1502 c 2002 b 31 402 d 3092

If resistance of 3T and reactance of 4 are connected in a c circuit then power factor of circuit will be 31 Options 0 8 0 6 1 33

An L C circuit oscillates at frequency of 100 Hz At t 0 the capacitor of 4 F is charged to 5 C and current in circuit is zero The current in circuit when energy is equally stored in capacitor and inductor is mA C 11 mm

21 A device X is connected to an a c source The variation of vo power in one complete cycle is shown in Fig 75 7 28 1MW power 10 km away al Which curve shows power consumption over a full cycle b What is the average power consumption over a cycle c Identify the device X purpose C transmitted Zero Inductor or capaator are the answe B1 KM TUM IN Fig 7 5 1 power doing ii a step 11000 used Pcu 7 29 Conside curren

Q 26 A LCR circuit is connected in series If at resonance it has L 150pH and C 200PF Then calculate band width A 0 2 X 10 radian sec B 15X10 radian sec C 6 6X 10 radian sec D 5 X 10 radian sec

d 5 2 A 2 An alternating current generator has an internal resistance Rg and an internal reactance Xg It is used to supply power to a passive load consisting of a resistance Rg and a reactance X For maximum power to be delivered from the generator to the load the value of X is equal to a zero b X c X d R

4 For the circuit given below assume that 100 Vr 25 mV VCE SAT 0 2 V and VBE VD 0 7 V Find the collector currents of both transistors and the values for the labeled voltages V V V3 V4 and Vs Do not forget to verify your assumptions Numerical solution V 2 41V V3 2 17V and V5 6 82V Vcc 9 V V R 80 kn D R 40 kn V4 V Rc1 2 kn D Q RE 2 kn W RE1 2 kn RE2 100 0 V5 V3 Rc2 100 0

Current in an AC circuit is given by i 3 sin oot 4 cos cot Then A rms value of current is 5A 55A x B C D 6 mean value of this current in positive one half period will be A I if voltage applied is V Vsinot then the circuit must be containing resistance and capacitance if voltage applied is V Vmcosoot then the circuit may contain resistance and inductance only 28

3 A battery is charged at a potential of 15 V for 8 h when the current flowing is 10 A The battery on discharge supplies a current of 5 A for 15 h The mean terminal voltage during discharge is 14 V The watt hour efficiency of the battery is 1 82 5 2 90 3 80

It is desired to set up an undriven L C circuit in which the capacitor is originally charged to potential difference of 100 0 V The maximum curren is to be 1 0 A and the oscillation frequency is to be 1000 Hz What are the required values of L and C

A 750Hz 20 V rms source is connected to a resistance of 100 S2 an inductance of 0 1803 H and a capacitance of 10 F all in series The time in which the resistance heat capacity 2 J C will get heated by 10 C Assume no loss of heat to the surroudings is close to JEE Main 2020 September 1 348 s 2 418 s

A thin superconducting zero resistance ring is held above a vertical long solenoid as shown in the figure The axis of symmetry of the ring is same to that of the solenoid The cylindrically symmetric magnetic field around the ring can be described approximately in terms of the vertical and radial component of the magnetic field vector as B Bo 1 az and B Bo r where Bo a and B are constants and z r are vertical and radial position coordinates respectively Initially plane of the ring is horizontal has no current flowing in it When released it starts to move downwards with its axis still vertical Initial coordinates of the centre of the ring is z 0 and r 0 In the given diagram point O is on the axis and slightly above the solenoid having vertical and radial position coordinates as 0 0 Ring has mass m radius ro and self inductance L Assume the acceleration due to gravity as g 1 Find the magnitude of current in the ring at a vertical position z A Banr z L B rz C 2L B Baz D None of these Voltage Source 0 r c

4 A simple ac circuit is composed of a capacitor connected across the terminals of an ac power source If the frequency of the source is doubled what happens to the reactance of the capacitor A It increases by a factor of 4 B It increases by a factor of 2 C It decreases by a factor of 2 D It decreases by a factor of 4

A series LCR circuit containing 5 0 H inductor 80 F capacitor and 40 resistor is connected to 230 V variable frequency ac source The angular frequencies of the source at which power transferred to the circuit is half the power at the resonant angular frequency are likely to be 42 rad s and 58 rad s 25 rad s and 75 rad s 50 rad s and 25 rad s 46 rad s and 54 rad s 1 2 3 4

An ac source of angular frequency is across a resistor r and a capacitor C in se The current in the circuit measured is 1 If nov requency of source is changed to o 3 maintaining the same voltage the current in circuit is found to reduce by a factor of three xower factor of the circuit at the ori requency to is 1 1 3 Zoro 2 1 2 4 1 3

A small metallic ball is charged positively and negatively in a sinusoidal manner at a frequency of 10 aps The maximum charge on the ball is 10 6 C What is the maximum displacement current due to this alternating current 1 2 3 4 orrect Answer 1 catu unattempted Add to Bookmark List 6 28 amp 34 amp 3 75 104 amp 12 56 amp