AC Circuits Questions and Answers

What is the time constant for a series RC circuit hooked up to and emf of V when the resistance is given to be 73 kn and the capacitance is given by 687 pF Give your answer in microsecon T Part B Suppose you connect this capacitor in series with a capacitor with C 3840 pF and this combination is in series with the same resistor above What now is the time constant in us T US Part C us Suppose you connect those two capacitors in parallel and this combination is in series with the same resistor above What now is the time constant in us

An electric lamp which runs at 80 V DC consumes 10 A current The lamp is connected to 100 V 50 Hz ac source compute the inductance of the choke required to keep same current through lamp Question Type Single Correct Type 1 0 2 H 2 2 3 0 02 H

In an ac circuit the readings of ammeter and voltmeter are 10 A and 25 V respectively Power in the circuit will be O More than 250 W Always less than 250 W O 250 W O Less than or equal to 250 W Marks 4 1

At a moment t 0 when the charge on capacitor C is zero the switch is closed If lo be the current through inductor at t 0 for t 0 C L momon C S 1 maximum current through inductor equals lo 2 C Io 2 maximum current through inductor equals C C2 3 maximum charge on C C L0VLC C C 4 maximum charge on C C I0 L CLC

Two coils A and B are connected in series with a supply of 240V 50Hz A s resistance is 5 ohm and B s inductance is 0 02 H the decayed power is 3KW and the power coefficient is 75 then find the inductance of coil A

ampere d 5 0 ampere The diagram below shows two coils A and B placed parallel to each other at a very small distance Coil A is connected to an ac supply G is a very sensitive galvanometer When the key is closed DCE 2006 K 00 A B G a Constant deflection will be observed in the TV galvanometer for 50 Hz supply b Visible small variations will be observed in the galvanometer for 50 Hz input c Oscillations in the galvanometer may be observed when the input ac voltage has a frequency of 1 to 2 Hz d No variation will be observed in the galvanometer even when the input ac voltage is 1 or 2 Hz f th proa

A simple a c as shown in figure i 201 1 0 W emf V 1 0 2 0 Figure 1 If the speed of the coil is changed then the graph of the new output is shown in figure ii 4 Time s 1 01 4 Time s Figure ii 19 What change does occur in the speed of the coll

Find the terminal voltage and resistance of the load The de shunt generator deliver power to the load of last four digits of your enrolment number W whose externa characteristics is given as V 0 3 IL 150

Two capacitors C and C are charged to 120 V and 200 V respectively It is found that connecting them together the potential on each one can be made zero Then A5C1 3C B 3C1 5C

A 250 V 12 000 W 3000 rpm de shunt motor has Rf Ra and full load efficiency of 120 N 0 35 and 85 respectively Determine the external resistance added to the armature circuit to bring the speed to last four digits of your enrolment number rpm Consider load torque is independent of speed

A 1 transformer has Z 20 j80 Z 0 04 j0 2 and turns ratio of 30 1 espectively Flux lags the no load current Io 1 8 A by 30 degree The secondary ide of the transformer delivers a current of 180 A at a terminal voltage of 9th 10th 1th digits of your enrolment number V and 0 8 pf leading Determine the primary voltage with the help of vector diagram

Which one of the following statements is not correct 1 A diode does not obey Ohm s law 2 A PN junction diode symbol shows an arrow identifying the direction of current forward flow 3 An ideal diode is an open switch 4 An ideal diode is an ideal one way conductor

Implement the following Boolean function using PAL with four inputs and 3 wire AND O structure Also write PAL programming table Fi A B C D Em 2 12 13 F2 A B C D m 7 8 9 10 11 12 13 14 15 F3 A B C D m 0 2 3 4 5 6 7 8 10 11 15 F4 A B C D Em 1 2 8 12 13

In the inductive circuit given in the figure the current rises after the switch is put on At instant when the current is 15 mA then potential difference across the inductor will be 4000 22 ww A B C D Zero 240 V 180 V 60 V 12 mH m 240V

47 electrical energy with time is correctly shown If charge in Q capacitor varies as 0 0 in LC oscillation U 1 1 2 3 U T 2T U mm T 2T t pas t 2T AV VA 2T

A parallel AC circuit has two branches One branch contains a resistance of 8 ohm inductance of 19 1 mH in series and the other branch contains a resistance of 6 ohms and a capacitor of capacitance 601 55 F in series This parallel circuit is connected across a supply voltage of 240V 50Hz Determine current drawn by each branch and total current drawn from mains and power factor of whole circuit Solve using admittance method only 5

In the following circuit the potential of source i E 200 volt R 2002 L 0 1 H C 10 6 fara and frequency is variable then the current a f 0 and f is R www 1 0 amp 10 amp 3 10 amp 10 omn L C moon 2 10 amp 0 amp mp mp

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 Q i reeeeeeee 1 i as well as Q increasing 2 i as well as Q decreasing 3 i is increasing but Q is decreasing 4 iis decreasing but Q is increasing

7 An L R C series circuit consists of an a c voltage supply with an amplitude of 120 V at an angular frequency of 60 rad s a 335 2 resistor a 2 88 H inductor and a variable capacitor a At what capacitance will the current amplitude in the circuit be a maximum b With the capacitance found in part a what will the voltage amplitude across the inductor be

LCR circuit is analogous to driving force F t mechanics 1 Current dq dt here q is the charge 2 Inductance L 3 Capacitance C 4 Walte 1 1

Three identical resistors each of value 402 are connected first in star and then in delta across a 200 V three phase 50 Hz supply Calculate the power taken from the supply in each case 4 CO2

The primary coil of a transformer has 425 turns the secondary coil has 1000 turns An alternating current is sent through the primary coil The emf in the primary is of amplitude 19 0 V What is the emf amplitude in the secondary V

b Two current i 50 Sin cot i 95 Sin oot 450 are flowing through a common conductor Find an expression for the total current in similar form Find also the r m s value of the current 4

Phase of current in LC 1 Is in the phase of potential 2 Leading from the phase of potential 3 Lagging from the phase of potential 4 Before resonance frequency leading from th phase of potential and after resonanc frequency lagging from the phase of potenti

An ac generator with a frequency of 125 Hz and an rms voltage of 42 5 V is connected in series with a 10 0 k resistor and a 0 250 micro Farad capacitor What is the rms current in this circuit 4 21 mA 3 79 MA 2 1 mA 5 mA

View in English A resistance of 400 a coil of inductive reactance 2002 and capacitor of capacitive reactance 50 0 are connected across 250 V mains in series The potential difference across the capacitor will be 250 V 50 V 200 V 100 V

An ideal choke draws a current of 8A when connected to an AC supply of 100 V 50 Hz A pure resistor draws a current of 10 A when connected to the same source The ideal choke and the resistor are connected in series and then connected to the AC source of 150 V 40 Hz The current in the circuit becomes 1 2 8 A 3 18 A

77 The input signal given to a CE amplifier having a voltage gain of 150 is V 2 cos 15t 151 corresponding output signal will be 2015 RS b c d 75 cos 15t 2tt 3 2 cos 15t ST 6 300 cos 15t 4 3 B C T 300 cos 15t The

42 A sinusoidal voltage of rms value 220 V is applied to a diode and a resistor R in the circuit shown in figure so that half wave rectification occurs If the diode is ideal what is the rms voltage across R plict a 55 2 V c 110 2 V R eller wwww R Output b 110 V d 220 2 V

36 A series L C R circuit is connected to an AC source Using the phasor diagram derive the expression for the impedance of the circuit Plot a graph to show the variation of current with frequency of the source explaining the nature of its variation

In an L C circuit consisting of 20 mH inductor and 0 1 F capacitor the maximum current in the circuit is 0 15A The maximum voltage across the capacitor is approximately 1 60 volt 3 67 volt 2 75 volt 4 57 volt

4 There is a 5 resistance in an A C circuit Inductance of 0 1 H is connected with it in series If equation of A C e m f is 5 sin 50 t then the phase difference between current and e m f is o AN 1 RIN 2 2 3 45 I 4 4 0 AC0035

64 When a DC voltage of 200V is applied to a coil of self inductance 2 3 H a current of 1A flows through it But by replacing DC source with AC source of 200V the current in the coil is reduced to 0 5A Then the frequency of AC supply is a 30 Hz b 60 Hz c 75 Hz d 50 Hz

An RLC series circuit has a 1 00 k2 resistor a 160 mH inductor and a 25 0 nF capacitor a Find the circuit s impedance at 502 Hz b If the voltage source has Vrms 408 V what is Irms mA c What is the resonant frequency of the circuit kHz d What is Irms at resonance

4 1 592 A battery of emf 10V is connected to resistance as shown in figure The potential difference V between the points A and B is 322 10V 1 2V 12 A 32 32 B 302 2 2V 3 5V 4 20 V

5 9 A 402 electric heater is connected to a 200 V 50 Hz mains supply The peak value of electric current flowing in the circuit is approximately A 2 5A C 7 A B 5 0 A D 10 A

An AC source with a maximum voltage of 125 V and F 55 0 Hz is connected between points a and d in the figure below Calculate the rms voltages between the following points G www 40 0 2 a a and b voo HH 185 mH 65 0 F b b and c Give your answer to at least the nearest volt c c and d Give your answer to at least the nearest volt d band d

5 2 The potential difference V and the current i flowing through an instrument in an AC circuit of frequency f are given as V cos oot volts and i 2sinot amperes The power dissipated in the instrument is A Zero C 5 W B 10 W D 2 5 W

A Coil of power factor 0 6 is in series with a 100 F when connected to a 5 Hz supply the p d across the coil is equal to p d across the capacitor Find th resistance and inductance of the coil of alternati

https rogo nottingham ac uk paper start php id 23949160977807391429 dont record true 9 Which is the correct circuit to change an AC input to a smoothed DC output a full wave smoothed rectifier R Vin Vin Vin Vin D D D D3 DA D DA D DA DA II D C C Vout Vout Ba DA out Vout out

V R A circuit with a variable voltage source is constructed as diagrammed above At t 0 the switch is closed and the variable voltage source provides a consistent magnitude current out of its upper terminal by reactively adjusting its provided emf if and as necessary At what time s t 0 will the current through the resistor match the current through the inductor

5 30 In the circuit shown below what will be the readings of the voltmeter V3 and ammeter A vvvvvvv Vc referenc A 800 V 2A Je 220 V 2 2 A 300V HH V 300V 1000 Figure 5 294 V3 220V 50Hz B 300 V 2A D 100 V 2A

A Reconfigurable RCL Circuit A series RCL circuit is composed of a resistor R 220 two identical capacitors C 4 00 nF connected in series and two identical inductors L 6 20 x 10 5 H connected in series You and your team need to determine a the resonant frequency of this configuration b What are all of the other possible resonant frequencies that can be attained by reconfiguring the capacitors and inductors while using all of the components and keeping the proper series RCL order c If you were to design a circuit using only one of the given inductors and one adjustable capacitor what would the range of the variable capacitor need to be in order to cover all of the resonant frequencies found in a and b

An LCR series circuit containing a resistance of 1200 has angular resonance frequency 4 x 105 rad s 1 At resonance the voltage across resistance and inductance are 60V and 40V respectively The value of C IS 1 8x F x is

An alternating current varying sinusoidally at 50 Hz has its rms value of 10A Write down an equation for the instantaneous value of the current Find the value of the current at a 0 0025 second after passing through the positive maximum value

67 The LCR circuit shown below is driven by an voltage source a 1 VIC ww R 1 The angular frequency amplitude across the capacitor is a maximum is 000000 L R C C at which the voltage b d A 1 C I 1 PORTRA 1 R C 2L R C T

ALLEN 1 A circuit when connected to an AC source of 12 V gives a current of 0 2 A The same circuit when connected to a DC source of 12 V gives a current of 0 4 A The circuit is 1 series LR 2 series RC 3 series LC 4 series LCR A cycle wheel of radius 0 5 m is rotated with constant angular velocity of 10 rad s in a region of magnetic field of 0 1 T which is perpendicular to the plane of the wheel The EMF generated between its centre and the rim is 1 0 25 V 2 0 125 V 40 41

5 44 In the AC circuit shown in figure 5 299 the voltmeter whose reading will be zero at resonance is V V V ooooo 11 L C V Figure 5 299 P R B V D V

A 40 F capacitor is connected to a 200 V 50 ac supply The rms value of the current in t circuit is nearly 1 7 A 2 05 A 2 5 A 25 1 A 1 2 3 4

A sinusoidal voltage wave whose maximum value is V can be represented as ARS Vm 20 Im Ve All of these V Sin ot