AC Circuits Questions and Answers

When 100 V D C flows in a solenoid the current is 1 0 A When 100 V A C flows the current drops to 0 5 A If the frequency of A C be 50 Hz then the impedance and the inductance of the solenoid are A 200 S2 0 55 H B 100 2 0 86 H C D 200 S2 1 0 H 10092 0 93 H

An inductive coil has a resistance of 100 when an A C source of frequency 1000 Hz is applied across the coil The applied voltage leads the current by 45 The inductance of the coil is A 10 mH 16 mH B 12 mH 8 mH D

It is found that the current in the circuit is 0 50 A with D C source and 0 40 A with A C sources The voltage E for D C is 120 V and for A C is 120 V The frequency of A C source is 60 Hz The inductance of the circuit is B A 0 28 H C 0 60 H 0 80 H 0 48 H

A resistance of 10 2 an inductance of 2 henry and a capacitor of F are connected in series with mains line of 110 V and 50 Hz The phase difference between the voltage and current will be LEAT 90 C 0 B D T 90 180

An A C voltage of r m s value 0 1 V is applied to an LCR series circuit in which L 100 H and C 4 x 108 F and R 2 2 The resonant frequency will be 106 A Hz C TC SIR 5 T 10 Hz B L 104 T 25 T Hz 10 Hz

The r m s value of an A C of 50 Hz is 10 A The time taken by the alternating current in reaching from zero to maximum value and the peak value of current will be A 2 102 s and 14 14 A B 1 102 s and 7 07 A 2 C 5 x 103 s and 7 07 A 5 x 10 s and 14 14 A D

An alternating e m f of 100 V rms is applied to a series LCR circuit At resonance the potential difference across the inductance and across the capacitance is 400 V each The potential difference across the resistance will be A C 400 V zero 100 V 800 V B D

The impedence of a series LCR circuit varies with 4 frequency of applied voltage source as below ZA 32 Zo 0 o Identify the correct option 1 At current lags the source emf by radians 2 At w current leads the source emf by radians 3 w w 0 4 All of these 1 3 5 As rep voit 1

R A solenoid of inductance L and resistance is connected in parallel to a resistance R 2 An ideal battery of emf E is connected across the parallel combination as shown in figure Switch S is kept closed for long time and it is opened at time t 0 The current through solenoid immediately after switch opened is I and total heat generated in the solenoid after switch opened is H Then A I R SRAM 2E R B I L R 2 mmmm S 2 LE2 3 R C H YATI D H 2 R

Question No 42 Phy Section B This section contains 15 SINGLE CORRECT TYPE questions Out of these 15 questions candidate can choose to attempt any 10 questions A galvanometer has resistance 100 Q2 It gives full scale deflection on passing 10 mA current through it To convert it into voltmeter of range 0 to 10 V the resistance to be added in series is O 11100 O 900 O 90000 View In English O900 Q 180 41 46 61 66

3 8 KR T T 4 10m KR T T 0 Power dissipation through a resistor when an a source is connected is P If an inductor X 2 2R is connected in series with resist keeping source same power dissipation become 1 P AR 3 alm 4 None of these

33 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 If instead C is removed from the circuit the phase difference is again between current and voltage The power factor of the circuit is 71 3 1 1 0 3 0 5 2 zero 4 1 0 3

26 A series LCR circuit containing a resistance of 120 2 has angular resonance frequency 19 diri tellud ori 4 x 105rad s At resonance the voltage Srl to mais across resistance and inductance are 60 V and 40 V respectively At what frequency the current in the circuit lags the voltage by 45 Give answer in 105 rad s

8 A transformer has a primary coil with 1600 turns and a secondary coil with 1200 turns If the current in the primary coil is 6 Ampere then what is the current in the secondary coil of a transformer 4 5 A 8 A O4 A O 10 A

5 A transformer is used to convert O Mechanical energy into electrical energy Electrical energy into mechanical energy High or low voltage d c into low or high voltage d c High or low voltage a c into low or high voltage a c

A coil has a resistance of 40 and an inductance of 9 55mH connected to a 240V 50 Hz upply Calculate 5 1 The inductive reactance 2 The impedance 3 The current taken from the supply A capacitor of 23 F connected to a 240V 50Hz Supply Calculate 1 2 3 The capacitive reactance The impedance The current taken from the supply

Revisit An AC supply of 230 volt is applied to a half wave rectifier circuit Find I Output DC voltage il Rectification efficiency 2 marks CO4 Choose the best option 530 36 V 40 06 130 6 V 40 06 260 36 V 80 06 103 6 V 80 06

An inductor 4H and a resistance 50 are connected in series with an A C source At a particular instant voltage across inductor is 3 volt and across resistor is 4 volt For that particular instant choose correct options A Voltage across source is 5 volt B Voltage across source may be 7 volt C voltage across source may be 1 volt circuit is 08 Amp

Figure a shows plot of voltage across the capacitor as a function of the driving frequency for a sinusoidally driven electromagnetic oscillator LCR circuit Figure b shows phase angle phase difference between voltage and current vs olo graph for same circuit for three different quality factor graph 1 2 3 of figure a and each one can be matched by one of graphs a b c also of figure b 1 2 c w C figure a figure b A Graph 3 corresponds to graph a B Graph 1 corresponds to graph c 6 0 C The circuit of graph 1 has high quality factor D The circuit of graph 3 has high quality factor

A series RLC circuit is activated by a frequency o variable ac source of voltage V volt as shown in the circuit VRL and V are the potential drops across RL and C respectively Select the incorrect statement s C A At low frequency limit both V RL R www L 60000000 and V are proportional to o C C At high frequency limit both V RL B At high frequency limit V approaches V but Vis proportional to S 1 2 O 1 9 and V are proportional to C frequency limit V is proportional to o whereas V approaches V

In the following circuit the AC source is an ideal voltage source What is the amplitude of the steady state current through the inductor at resonance A 0 C Vo C R C 2L B Vo C D V VO V V sin ot R www

4 Resonance in series LCR circuit is also used in tuning mechanism of TV sets Which of the following combinations should be selected for better tuning of an L C R circuit used for communication a R 20 2 L 1 3H C 35 F b R 25 12 L 23 H C 45 F d R 25 12 L 1 5 H C 45 pf c R 1502 L 3 5H C 30 F As the freemene of an ae cirenit increases the current first increases and then decrease What

b A 200 50V 50 Hz single phase transformer is connected to a 200V 50 Hz supply with secondary winding open 1 What is the value of maximum flux through the core if the primary winding has 400 turns ii What is the peak value of flux if the primary voltage is 200V 25 Hz and what happens to no load current

Specimen Numerical A coil of inductance 1 H and negligible resistance is connected to a 120 V mains supply Find the current flowing in the circuit if the frequency of the supply is 50 Hz If the inductance is changed to 3 H how much current will flow

54 In an ac circuit the applied voltage and the current flowing are E 110sin n t and I 11 sin nt n 3 respectively What is the power consumed in the circuit a zero b 605 W c 302 5W d 1210W

53 In an AC circuit consisting of a capacitor and a bulb how will the brightness of the bulb change if a dielectric is introduced between the plates of the capacitor a No change b Increases c Decreases d First decreases then increases

13 In a series RLC circuit the r m s voltage across the resistor and the inductor are respectively 400 V and 700 V If the equation for the applied voltage is 500 2 sinot then the peak voltage across the capacitor is 1 1200 V 2 1200 2 V 3 400 V R L C voooo 500 2sinot

1 he applied potential difference in the circuit shown is V 10 sin100t where Vis in volt and t is in second If the power factor of the circuit is hen the value of capacitance C of the circuit nearly is 0 1 H C HH vooroo 2002 wwwww V 10 sin 100t O 111 F O333 F O222 F

A coil and a bulb are connected in series with a de source A soft iron core is then inserted in the coil hen Intensity of the bulb remains the same Intensity of the bulb decreases Intensity of the bulb increases The bulb ceases to glow

In the circuit shown after sufficiently long time in position 1 of the switch so that current is steady in the circuit the switch is moved over to position 2 The maximum voltage that can be developed across L A 100 V B 100 2 V C 100 5 V D 200 V 100V 500 R E S 000000 S 100mH L 8 F

A resistance and a capacitor are connected to an ac source If the resistance increases then the average bpower liberated in the resistance Pick the most appropriate answer 1 Will increase 2 Will decrease 3 May increase or decrease 4 Will remain constant

The current I in an A C circuit with inductance coil varies with time according to the graph given below t Which one of the following graphs gives the variation of voltage with time b V a v c V d V

A pure inductor of inductance 0 7 H is connected in series with a resistance of 220 Q If an alternating emf of 440 V 50 Hz is applied to it 22 then the wattless component of current is 7 O 1 4 A 02A 01 A O A T

Two metal spheres of radius R are placed at a very large distance from each other and they are connected by a coil of inductance L as it is shown in the figure One of the spheres is loaded with electric charge I L v o o ovo The time period of the oscillatory circuit is A TELR C 3 E LR B 2 ELR 3 D TE LR V2

2 Alternating current of peak value TC flows through the primary coil of the coefficient of mutual A 100 V C 300 V ampere transformer The inductance between primary and secondary coil is 1 henry The peak e m f induced in secondary coil is Frequency of a c 50 Hz MHT CET 2016 200 V 400 V B D

A capacitor stores 10 C charge when connected across a battery When the gap between the plates is filled with a dielectric a charge of 20 C flows through the battery Fin the dielectric constant of the dielectric A K 2 B k 4 C k 3 D k 1

Two similar bulbs of rating 100W 50 2 V are connected in circuit as shown when frequency of source is varied brightness of B changes It is observed that a 50 hz frequency both the bulbs have same brightness Select correct alternative s He O V 100 sin 2 ft B B A Current in both the bulbs will be in same phase when both have same brightness B Current through source will be 2A when both the bulbs have same brightness C Current through source will be 2 2 A when both the bulbs have same brightness DYD will be more brighter for all frequencies except 50 Hz

A 10 0 mL solution of 0 050 M AgNO was titrated with 0 0250 M NaBr in the cell S C E titration solution Ag s Find the cell voltage for 30 0 mL of titrant A 0 093 V B 0 039 V C 0 093 V D 0 039 V

In this circuit given the value of R option L C iv Current through the source is A only iii and iv are correct R ww Consider the following statements and choose the correc R www i RMS value of current through a c source is ii Impedance of circuit is independent of o iii Impedance of circuit depends upon V rms R 0 L vooooo V 00 rms 2R B only ii is correct

alternating voltage sources 7 as shown in the figure where o and corresponds to 30 and 3 127 respectively Find the peak current in Amp through the resistor connected across a resistance R A 3 3sinot volt V 5sin ot volt and V3 5 sin oot vol 1 B 4 V C 5 7 39 D 6

For shown circuit XL 250 m RO 250V X 750 HH A Current in circuit is 10A B Voltage across inductor is 100V C Voltage across capacitor is 200V D Voltage on capacitor is more than that of supply voltage because the phase difference be

In the given L C R circuit the value of rms current through the a c source is L 000000 A C rms 2 R OL 0 1 C Vrms 2 R 0 LC OL VISO B D R ww R V rms OL 1 0 LC V rms 2 1 R OL C

9 A diode whose internal resistance is 20 2 is to supply power to a 1000 2 load from a 230 V rms source of supply Calculate a the peak load current b the de load current c the de diode voltage d the percentage regulation from no load to given load TAS 1983

questions from the codes a b c and d given below A Both A and R are true and R is the correct explanation of A B Both A and R are correct but R is not the correct explanation of A C Ais true and R is false D A and R both are false Q27 Assertion A An incandescent lamp is connected in series to a parallel plate capacitor and a supply The brightness of an electric incandescent increases when a dielectric slab is inserted between its plates Reason R Inserting dielectric slab between the plates of capacitor increases the impedance of circuit

1 A series R C circuit is connected across a source of emf V 100 2 sin 1000t where R 10009 and C 1 F The equation of current in the circuit is 1 i 0 1 sin 1000t 3 i 10 sin 1000t T 2 i 10 sin 1000t 4 TU 4 TO 4 i 0 1 sin 1000t

3 In the following circuit rms current through inductor is 0 8 A the rms current through capacitor is 0 4 A and rms current through resistor is 0 3 A the current delivered by a c source is 1 0 7 A 2 1 5 A 3 0 5A L voooo R www 41c

14 In the given A C circuit the through inductor and capacitor are 0 8 A and 0 4 A respectively The instantaneous current through resistor is 1 1 2 A 2 0 6 3 0 4 www L mwww C

NCERT Pg 245 1 For resonance the presence of both L and C elements in the circuit is must in LCR series circuit AC circuit 2 The power factor in a LCR series circuit is a measure of how close the circuit is to expending the maximum power 3 The quality factor is the measure of the sharpness of resonance in series RLC circuit 4 In a step up transformer voltage changes from low to high and the current is in same proportion

In the circuit shown in the figure the switch is initially at position 1 for a long time Now at t 0 the switch is turned to position 2 Initially charge on capacitor C is zero Choose the CORRECT statements A After the switch is thrown to position 2 the circuit performs LC oscillation with angular frequency 3 2LC B Just after the switch is turned the current through the circuit is D 4CE C The maximum charge in capacitor C is equal to 3 CE The maximum charge in capacitor C is equal to 3 2C 3L L 000000 C 2C 2 HHE 1

A current of 2 A is flowing at 220 V in the primary coil of a transformer If current in the secondary coil is 1 A and efficiency of the transformer is 80 then the voltage produced in the secondary coil wil be NCERT Pg 2607 1 176 V 2 352 V 3 528 V