AC Circuits Questions and Answers

Analyze a circuit in which there is a series combination of a resistance of 50 ohm and a capacitance of 2 micro farad This series combination is connected across 210 volt 50Hz ac supply What will be the power factor of the circuit A 0 314 lagging B 0 515 lagging 0 314 leading 0515 leading

A student designs a series RLC circuit in such a manner that it takes resistance of 500 capacitive reactance of 300 and inductive reactance of 600 Calculate the impedance and the power factor of the circuit A 60 32 ohms and 0 9 lagging B 60 32 ohms and 0 9 leading 58 31 ohms and 0 857 lagging 58 31 ohms and 0 857 leading hy

Q4 A capacitor having a capacitance of 20 F is connected in series with a non inductive resistance 1200 across a 100 volt 50 Hz supply Calculate i Phase difference between supply voltage and current ii Power

21 Alternating current is flowing in inductance L and resistance R The frequency of source is 0 2 Which of the following statement is correct 1 For low frequency the limiting value of impedance is L 2 For high frequency the limiting value of impedance is OL 3 For high frequency the limiting value of impedance is R 4 For low frequency the limiting value of impedance is L Z NODE02 BOAH AI TARGET PHY ENG MODULE 05 03 ALTERNATING CURRENT 02 B

A step up transformer has turn ratio 1 10 A cell of e m f 5 volts is fed to the primary Voltage developed in secondary coil is A B C 20 V 10 V 50 V Zero My Answer Correct Answer

48 The self inductance of the motor of an electric fan is 10 H In order to impart maximum power at 50Hz It should be connected to a capacitance of 1 2 x 10 F 2 3 10 F 3 10 F 4 10 F 49 In a series resonant R L C circuit hy 25 and C is decre

An alternating voltage source V 20 sin wt volt is applied across a circuit The resulting current from the source is found to be i 10 sin ot sin 3 The average power consumption is 50 W 20 W 6 W

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

Variation of a current with time is shown in the graph below The rms value of the current between time t 0 to t 4 sis i 37 4 2 A 3 A 5 A 3 A t

An AC circuit having supply voltage V consists of resistor of resistance 4 Q and capacitor of reactance 3 0 as shown in the figure The voltage across the capacitor at time t is R www 9 6 V V 20 sin of 12 4 V Zero Xc H S

A step down transformer reduces the voltage of transmission line from 2200 V to 220 V The power delivere by it is 8800 W and its efficiency is 88 The input current is 4 55 A 1 75 A 3 67 A

The power factor of the circuit shown in the figure is Xc 40 S2 HH 220 V 50 Hz 0 2 0 4 0 8 0 6 mmmmm X 100 wwwww R 80 92

An LCR series circuit with 100 W resistance is connected to an ac source o 400 V and angular frequency 300 rad s When only the capacitance is removed the current lags behind the voltage by 60 When only the inductance is removed the current leads the voltage by 60 The power in watt dissipated in the LCE circuit is 400 x value of x is

The voltage across a load and the current through the element is given by v t 60 cos wt 10 volts i t 1 5 cos wt 50 Amps Find 1 Apparent Power 2 True Power 3 Reactive Power 4 Power factor 5 Load impedance

Two plates of a capacitor of capacitance C are given charges Q and Q This capacitor is connected across a resistance R Key is closed at t 0 Which option s are correct 1 enc 2 2 A Charge on the outer surface of plates change after closing the key B Charge on the outer surface of plats does not change when discharge C At t Seconds total charge on the left plate when discharge is 9 Q Q 2 D At t Seconds total charge on the right plate when discharge is Q 0 G 9 RC Q 1 0

An alternating current is given by I 50 sin 100 t Find the frequency of current mean current during a positive half cycle virtual current and the current at t 1 300 s Ans 50 Hz 31 8 A 35 4 A 43 3 A

8 If resistance R 1000 inductance L H and capacitance c F are connected in series with an AC source of 200 volt and frequency f as shown in the circuit If the readings of the hot wire voltmeters V and V are same then which among the following statements is wrong A B f 125 Hz f 250 Hz Current through R is 2A V V 1000 volt R wwwmooooo

Q No 21 Single Correct A A The power dissipated in the circuit Xc R A B C D NOW YOU YOU NOC 2R 5R 5R 10R R ww X 3R 0000 V V sin ot Marks 4 0

37 The effective value of current in the given ac circuit is X 592 000000 1 10 A 2 10 2 A 3 5 2 A 4 Zero R 50 www X 592 V E 50 2 sin 100 t

A capacitor C 2uF and an inductor with L 10 H and coil resistance 5 2 are in series in a circuit When an alternating current of r m s value 2A flows in the circuit the average power in watts in the circuit is 1 100 3 20 4 10 2 50

A student is working on a circuit in which a resistance of 1002 is connected in series with an inductance across 200V 50Hz in such a way that it takes 5A current 1 Measure the value of inductance of entire circuit 2 Observe the nature of inductive circuit with determination of power factor

For the circuit shown column II gives data for quantities given in column I Match them correctly A Column Reactance of circuit Impedance of circuit B C Current D Reading of V 4 p 9 r s 4 2 1 H 00000000 V 200V 50 Hz V4 100 Q V Column Il 100 2 100 200 2 None of these V 100 TH V3

In a LCR circuit half power frequencies frequency at which power dissipated is half the maximum power drissipated in the circuit are found to be 90 rad s and rad s Then the value of quality factor is

The rms value of current given by equation 2 4 sinw A for a complete cycle is given by 2 A 4 A 2 3 A 4 3 A

In an LCR series circuit R 10 Q XL 20 Q and Xc 10 Q The average value of current for a complete cycle for source voltage V 20 sin 30t is 2 A 0 5 A 3 A

23 A capacitor C 2 F and an inductor with L 10 E and coil resistance 5 Q are in series in a circuit Whe an alternating current of r m s value 2A flows in th circuit the average power in watts in the circuit is A 100 C 20 B 50 D 10

The charge on the capacitor in LC circuit is given by d Q dt equation oscillation 2 Hz T 2 Hz 4 Hz 4 T Hz 16Q 0 Find the frequency of LC

The r m s value of current from t 0 to t 3 s for the curren i 3t A is 2 A 1 45 A hr min 4 A

Given an RLC series circuit with inductance of 0 25 henries resistance of 20 ohms capacitance of 1 300 farads and an electromotive force of 8e t volts determine the charge on the capacitor at any time t and the current at any time t

4 An inductance of 3 0 mH has a voltage that is described as follows for 0 1 2 ms V 15 0 V and for 2 t 4 ms V 30 0 V Obtain the corresponding current and sketch u and i for the given intervals

7 An AC voltage source described by V 10 cos 2 t is connected to a 1 F capacitor as show figure The key K is closed at t 0 The time t 0 after which the magnitude of curre reaches its maximum value for the first time is a is c 3 s V 10 cos K b 2 s d 4 s C 1 F

19 In the circuit shown in figure V V VV and V are ideal ac voltmeters The column I gives a condition and the column II gives the match the following A B 6 D www R 100002 SRAMAY 2000 V sin 1000 s COLUMN I When L I H and C 1 reading is approximately 1414V for When L 2 H and CF reading is 1000 V for When L1 H and 0 5pF reading is 1000 V for When L 2 H and C 0 5uF reading is non zero for P V 9 R COLUMN II S V 10 36 T V 40

When a and 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

Phy Section B This section contains 15 SINGLE CORRECT TYPE questions Out of these 15 questions candidate A charged capacitor of capacity 30 F is connected to 27 mH inductor What is angular frequency of free oscillations of the circuit O 1500 rad s 1 1111 rad s 1 Read More 1616 rad s 1

3 LEN Which of the following combinations should be 23 selected for better tuning of an L C R circuit used for communication 1 R 152 L 3 5 H C 30 F 2 R 25 52 L 1 5 H C 45 F 3 R 20 2 L 1 5 H C 35 F 4 R 25 02 L 2 5 H C 45 F RfL C R zyfin fery fafafora 1 R 15 22 L 3 5 H C 30 F 2 R 25 02 L 1 5 H C 45 F 3 R 20 02 L 1 5 H C 35 F 4 R 25 2 L 2 5 H C 45 F

35 The charge on the d Q d12 by equation of LC oscillation oscillat 1 2 x Hz 2 2 Hz 4 4 x Hz 36 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 Jo 3 4 Hz wwwww E R LC 3 LC E 1 in LC circuit is given 16Q 0 Find the frequency 000 2 2 LC 4 C R E R F LC

c An LCR series ac circuit is at resonance with 10 V each across L C and R If the resistance is halved the respective voltages across L C and R are a 10 V 10 V and 5 V c 20 V 20 V and 5 V e 5 V 5 V and 5 V Kerala PET 2010 b 10 V 10 V and 10 V d 20 V 20 V and 10 V ircuit is f If the capacitance is

Please deduce the equation Nce rt Pg 258 A m a a a b Replace each parameter in the above equation by the corresponding electrical quantity and see what happens Eliminate L C a and o using X L X 1 0C and 1 LC When you use Eqs 7 33 and 7 34 you will see that there is a perfect match

A uniformly wound solenoid coil of self inductance 1 8 10 H and resistance 62 is broken up into two identical coils These identical coils are then connected in parallel across a 12 V battery of negligible resistance The time constant for the current in the circuit is AMU Engg 2009 a 0 1 10 S b 0 2x10 S c 0 3 10 s d 0 4 10 s

a What do you understand by cut off frequency in relation to a parallel R L C resonant circuit Explain with respect to its current response Why is it called 3 dB frequency Justify b What is voltage magnification in a resonant circuit Prove that the voltage in the inductor and capacitor is magnified by Q times where Q is the quality factor 4 3

The r m s value of current for one time period in the above diagram which is plotted between i and t is A 4 2 0 4 10 s Corporate Office Aakash Tower

6 a A three phase 400 V 50 Hz a c supply is feeding a three phase delta connected load with each phase having a resistance of 25 ohms an inductance of 0 15 H and a capacitor of 120 microfarads in series Determine the line current volt amp active power and reactive volt amp 5

6 b A star connected balanced load is supplied from a 3 phase balanced supply with a line voltage of 416 V at a frequency of 50 Hz Each phase of load consists of a resistance and a capacitor joined in series and the readings on two watt meters connected to measure the total power supplied are 782 W and 1980 W both positive Calculate 1 the power factor of the circuit ii the line current and iii the capacitance of each capacitor

If there were two transformers one of high rating and one of low rating say one is of 50KV and one is of 5KV then how can we share the load among these two transformers On what factor load sharing is dependent among these transformers

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

1 At angular frequency 10 rad s the nature of circuit b Capacitive a Inductive c Resistive d M 2 Same current is flowing in two alternating circuits The first circuit contains only indu

For the shown AC circuit answer the following question Xc 492 HH www R 30 mm X 89 V 100sin 100 t volt Q Current drawn from the source as a function of time t is given as

r Anp njunction D shown in the figure can act as a rectifier An alternating current source V is connected in the circuit The current I in the resistor R can be shown by hrobr be 2 m 1 3 ww 4 AIEEE 2009 SC0056

0 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 b 1 2 c 2n d None of these

26 A condenser of capacity 20 F is first charged and then discharged through a 10 mH inductor Neglecting the resistance of the coil the frequency of the resulting vibrations will be a 356 cycles s b 35 6 cycles s c 356x10 cycles s d 3 56 cycles s