AC Circuits Questions and Answers

5 39 In the steady state condition the rate of heat produced in a choke coil is P The time constant of the choke coil it t If now the choke coil is short circuited then the total heat dissipated in the coil is A Pr C Pr In 2 2 Liv B P LAB D Pt ln 2 e 1 2 L RY P P2R

The self inductance of the motor of an electric fan is 10H In order to impart maximum power at 50 Hz it should be connected to a capacitance of 1 4 F 2 8 F 4 2 F 3 1 F

In a series LCR circuit the voltage across R is 100V and R 1 k2 C 2 F The resonant frequency w is 200 rad s At resonance the voltage across Lis 1 40 V 2 250 V 3 4 10 3 V 4 2 5 x 10 2 V

An ac voltage source of variable angular frequency and fixed amplitude Vo is connected in series with a capacitance C and an electric bulb of resistance R inductance zero When is increased 1 the bulb glows dimmer 2 the bulb glows brighter 3 total impedance of the circuit is unchanged 4 total impedance of the circuit increases

Mock Test Paper Code MTK 06 A sinusoidal a c current passes through a resistance R in LCR series circuit If phase difference between supplied voltage and supplied current is 8 and peak value of supplied current is lo then power dissipated in the circuit is 1 IR cose 2 1R 2 3 R IR cose 2

6 Comparing the L C oscillations with the oscillations of a spring block system force constant of spring k and mass of block m the physical quantity m and k are similar to 1 C and L 1 3 Cand 2 and 1 4 Land

F In the L C circuit shown in figure the current is in direction shown in the figure and charges on the capacitor plates have sign shown in the figure At this time Q i 4 relllllll L 1 i as well as Q increasing 2 i as well as Q decreasing 3 i is increasing but Q is decreasing

What is the frequency of power in an AC circuit connected to a capacitor Given f 30 Hz V 200 V 1 50 Hz 3 zero 2 100 Hz 4 60 Hz

16 An ac source of 200 V rms supplies active power of 600 W and reactive power of 800 VAR The rms current drawn from the source is

20 mA A group of electric lamps having a total power rating of 1000 watt is connected across an AC voltage 200sin 310t 60 where t in seconds gives in volts Then the rms value of the electric current radians is through source if it is known that the source emf leads current through itself by 3 alog ell A 1 10 amp 2 10 2 amp TU 3 20 amp 4 20 2 amp

The time constant of a circuit is 10 s when a resistance of 10 2 is connected in series in a previous circuit then time constant becomes 2 s then the self inductance of the circuit is

The relation between an A C voltage source and time in SI units is V 120 sin 100 t os 100 t volt value of peak voltage and frequency will be respectively 1 120 volt and 100 Hz 2 4 120 2 volt and 100 Hz 3 60 volt and 200 Hz alt and 100 Ha 100 bris alloy OS

39 A choke coil and capacitor are connected in series and the current through the combination is maximum for AC of frequency n If they are connected in parallel at what frequency is the current through the combination minimum a n c 2n b n 2 d None of these

4 An electric current has both DC and AC components DC component of 8A and AC component is given as I 6 sinot So Ims value of resultant current is a 8 05 A b 9 05 A d 13 58 A c 11 58 A

8 A resistance is connected to a capacitor in AC and TU between current and the phase difference is 1 b 4 1 voltage When the same resistance is connected to an inductor phase difference becomes tan 2 Power factor of the circuit when both capacitor and inductor are connected to the resistance will be 1 a 1 d 2

6 The average power dissipated in a pure inductor of inductance L when an AC current is passing through it d zero b L c 2L a NI

An AC source is rated 220 V 50 Hz The average voltage is calculated in a time interval of 0 01 s It 1 must be zero 3 is never zero 10 The magnetic field energy in an inductor changes from maximum value to minimum value in 5 0 ms when connected to an AC source The frequency of the source 2 may be zero 4 is 200 2 v is 1 20 Hz 3 200 Hz An AC source producing emf cos 100 m t cos 500 t is connected in series with a capacitor and a resistor The steady state current in the circuit is found to be i i cos 100 m t i cos 500 m t Mizi 2 i i 2 50 Hz 4 500 Hz

In a series LCR circuit which is connected to an AC voltage source choose the incorrect statemen Algebraic sum of instantaneous voltage across L C R is a variable live 2 Vinst VLinst Vinst V Rinst V sourceinst 3 Voltage across inductor capacitor resistance behave as a vector L 4 Current is same in inductor capacitor and resistance

Figure shows acceleration versus time graph of a particle starting from rest and moving along a straight line Which of the following statement s is are CORRECT a ms 25 t s 0 5 10 15 20 30 A The maximum velocity attained by the particle is 375 ms B The particle stops no where C The particle eventually moves with constant speed D The body gets retarded during the time interval 15 s t 30 s

In the given circuit the switch is closed at t 0 The ratio of electric current through resistance R at t 0 and at t 0 is R R R R ge002 www T R R

If E 100 sin 100t volt and I 100 sin 100t 73m mA are the instantaneous values of voltage and current then the r m s values of voltage and current are respectively a 70 7V 70 7mA b 70 7V 70 7A c 141 4V 141 4mA d 141 4V 141 4A e 100V 100mA

10 1 0F condenser is charged to 50 volts The charging battery is than disconnected and a 10 mH coil is connected across the capacitor so that LC oscillations occur What is the maximum current in the coil Assume that the circuit contains no resistance a 0 25 A b 0 50 A c 0 75 A d 1 00 A

A 100 32 resistance and a capacitor of 100 Q reactance are connected in series across a 220 V source When the capacitor is 50 charged the peak value of the displacement current is a 2 2 A b 11 A c 4 4 A d 11 2 A NEFT 11 2016

the value of R iv Current through the source is c option i RMS value of current through a c source is ii Impedance of circuit is independent of o iii Impedance of circuit depends upon o and liv are correct Consider the following statements and choose the correc R 0 L ww R ww rms 2R 000000 w 2 22 Jan 0 wl R R enthecae Vm0 Ams B only ii is correct C R Jan 1 C

In the circuit shown calculate the current I 5 Points E 100 V 20 T R ww 4 92 R Xc XL 69 000 190 70 R 802

ation of EMF with time for four types of generators are shown in the figures Which amongst them can be called AC NEET 2019 Odisha EA a c E EA 4 1 Only a 3 a b c d b d EA 2 a and d 4 a and b

The potential barrier existing across an unbiased p n junction is 0 2 volt What minimum kinetic energ hould have to diffuse from the p side to the n side if The junction is unbiased The junction is reverse biased at 0 1 volt a b The junction is forward biased at 0 1 volt

3 The input signal given to a CE amplifier having T a voltage gain of 150 is V 2 cos 15t 05 15 3 The corresponding output signal will be a 2 cos 15t 5T 6 b 300 cos 15t 4 3 c 300 cos 15t 3 2 d 75 cos 15t 2 2015

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 Current through resistor is i and voltage across capacitor is V then Re AIPMT 2015 1 V V 3 V V 2 V V 4 i i

The A C circuit shown in figure Find the frequency of the AC voltage source so that current through the source will be in same phase as of voltage of source A 1 R VLC L B 0 R LC L C o IC D JLC 1 LC R R 4L 2L

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

supply voltage is V Vosin 100nt 40V Z 502 and R 40 Then match the column L II V voodoo L C connected to an ac source the 7 V 40 V Column I A Peak current in A B V in volts C Effective value of applied voltage in volts VR R 1 2 3 Column II 10 2 50 2 50 D Xc in 4 1 a A 1 B 2 C 1 D 4 b A 2 B 3 C 1 D 4 a A 1 B 3 C D 1

2 4 A direct current of 5 A is superimposed on an alternating current 10 sinot flowing through a wire The effective value of the resulting current will be 1 7 5 A 2 2 3 A 3 5 3 A 1 15 A

32 To get steady DC output from pulsating voltage output of Rectifer we connect 1 Capacitor in parallel or inductor in series with Load R 2 Capacitor in series or inductor in parallel with Load R 3 Capacitor or inductor in series with Load R 4 Capacitor or inductor in parallel with Load R

2 The electric current in a circuit is given by i i t t for some time Calculate the rms current for the period t 0 to t t

If an A C main supply is given to be 220 V What would be the average e m f during a positive half cycle 1 198 V 2 386 V 3 256 V 4 None of these

4 In the circuit shown resistance reactance of R L respectively The and C are 40 92 80 2 and 50 supply emf is 250 V 50 Hz AC The RMS current flowing in the circuit is R L wwwmmmm 1 5 2 A ch 250 V 50 Hz tions 2 5 A C

A variable emf device V is applied across the series combination of resistance R and capacitor C such that the potential difference across resistance VR with time as shown in the graph Choose the correct graph depicting the variation of potential difference across capacitor Vc as a function of time A C Vc Vc T 2T 3T 4T 5T T 2T 3T 4T t B D Vet Vc VR wwwww R C T 2T 3T I 1 4T 1 I VR 2Vol T 2T 3T 4T ST T 2T t 3T

13 The current drawn by the primary coil of a transformer which steps down 220 V impedance of 220 V is

In series RLC circuit at resonance condition find average energy stored in inductor where peak voltage of source is 10 volt R 10 22 C 1 F mal L 1H 1 0 5 J 3 4 T 2 0 25 J 4 None

A capacitor of capacitance C and an ideal inductor of inductance L are connected in series with ideal battery of emf E The resistance of circuit is negligible If initially capacitor is uncharged and is closed at t 0 then select the correct statements L 0000000 AXMaximum charge on capacitor is CE B Maximum charge on capacitor is 2CE C Maximum potential difference across inductor is E D Maximum potential difference across inductor is 2E

Current Electricity N For the circuit shown in figure find the voltage across 102 resistor and the current passing through it KC7 55 10 210 A 20 current source 125A current source

37 An AC source is rated 220 V 50 Hz The average voltage calculated in time interval of 0 01 s 1 May be zero 2 Must be zero 3 Is never zero 220 4 Is volt 2

In an AC circuit voltage V Vosinot and inducto L is connected across the circuit Then th instantaneous power will be Vinzult Lo V 1 sinot 20L 0 3 0 20L sin 2ot 2 4 V 0 20L 0 Ol sinot sin 2ot

coil of self inductance L is connected in series with a bulb B and an AC source Brightness of the bulb decrease when NEET 2013 1 Number of turns in the coil is reduced 2 A capacitance of reactance X X is included in the same circuit 3 An iron rod is inserted in the coil 4 Frequency of the AC source is decreased

Switch is closed at t 0 then current in the circuit L 2R at t 1 R is R roos www E 2 1093 S 8 R L

A L R combination is connected to a battery of emf 4 volt If L 0 1 H and R 4 0 92 then the time taken to reach a current of 0 6321 ampere is 1 1 40 sec 3 1 6 sec 2 0 4 sec 4 0 63 sec

resistance and a capacitor of 100 reactance are connected in series across a 220 V source When the capacitor is 50 charged the peak value of the displacement current is 1 44 A 3 2 2 A 2 11 2 A 4 11 A 220 1100

Figure shows an L R circuit When the switch S is closed the current through resistor R R and R are 1 12 and I respectively The value of 1 12 and 1 at t 0 s is 1 1 2 1 4 Y 12 S 1 1 1 1 0 R www E E 2 13 0 R 1 R L E E 13 0 3 4 0 12 12 4 1 R R3 E wwww R 1 1 3 elle L E

A capacitor in an LC oscillator has a maximum potential difference of 15 V and maximum energy of 360 J At a certain instant the energy in the capacitor is 40 uJ At that instant emf induced in the inductor will be volt