Practice Test

Q1) The energy stored in an inductance is 1 joule when a current of 0.1 ampere is established in it. The self - inductance of the coil is Show Answer

Q2) The areas of cross-section of two solenoids A and B of equal length are equal but the number of turns in the solenoid A is double than that of B. If the coefficient of self-induction of B is 6 mH, then the coefficient of self-induction of A will be Show Answer

Q3) A copper ring is held horizontally and a bar magnet is dropped through the ring with its length along the axis of the ring. The acceleration of the falling magnet is Show Answer

Q4) Keeping all other factors same, the number of turns of a coil is doubled. The magnetic flux linked with the coil is Show Answer

Q5) Induction furnace is based on the heating effect of Show Answer

Q6) Lenz's law is consequence of the law of conservation of Show Answer

Q7) An artificial satellite with a metal surface is moving about the earth in a circular orbit. A current will be induced in the satellite, if Show Answer

Q8) A solenoid has n turns. If coefficient of self inductance L varies with n as Show Answer

Q9) A conducting rod PQ moves parallel to x-axis in a uniform magnetic field, pointing in the negative z-direction. The end P of the rod gets Show Answer

Q10) Which of the following statements is correct ? Show Answer

Q11) A circular coil of radius 5 cm has 500 turns of a wire. The approximate value of the coefficient of self-induction of the coil will be Show Answer

Q12) A rod of length 20 cm is rotating with angular speed of 100 revolutions per minute in a magnetic field of strength 0.5 T. What is the potential difference between two ends of the rod ? Show Answer

Q13) The coefficient of mutual - inductance of two circuits A and B is 3 mH and their respective resistance are 10 ohm and 4 ohm. How much current should change in 0.02 second in the circuit A, so that the induced current in B should be 0.006 ampere ? Show Answer

Q14) A coil whose diameter is 0.40 m is in a variable magnetic field. As the magnetic induction of the field changes by 127.4 T during 2 s, an emf of 200 V is induced in the coil. Then the number of turns in the coil is approximately Show Answer

Q15) An emf of 6 V is introduced in a given coil when the current in it changes at the rate of 30 A/min. The inductance of the coil is Show Answer

Q16) When the number o turns in a coil is doubled without any change in the length of the coil, its self-inductance becomes Show Answer

Q17) In a circular conducting coil, when current increases from 2 A to 18 A in 0.05 s, the induced emf is 20 V. The self-inductance of the coil is Show Answer

Q18) Which of the statements, about a solenoid, is correct ? Show Answer

Q19) A metallic rod of 1 m length is rotated with a frequency of 50 rev/s with one end hinged at the centre and the other end at the circumference of circular metallic ring of radius 1 m, about an axis passing through the centre and perpendicular to the plane of the ring. A constant and uniform magnetic field of 1 T parallel to the axis is present everywhere. The emf between the centre and the metallic ring is Show Answer

Q20) The expression for the magnetic energy stored in a solenoid in terms of magnetic field B, area A and length l of the solenoid is Show Answer

Q21) Current in a circuit falls from 5 A to 0 A 0.1 s. If an average emf of 200 V is induced, give an estimate of the self-inductance of the circuit Show Answer

Q22) A pair of adjacent coils has a mutual inductance of 1.5 H. If the current in one coil changes from 0 to 20 A in 0.5 s, what is the change of flux linkage with the other coil Show Answer

Q23) A light bulb is rated at 100 W for a 220 V supply. The peak voltage of the source is Show Answer

Q24) A pure inductor of 25 mH is connected to a source of 220 V. Find the rms current in the circuit if the frequency of the source is 50 Hz. Show Answer

Q25) Suppose the frequency of the source in the previous questions can be varied, what is the frequency at which resonance occurs ? Show Answer

Q26) The quality factor of an LCR circuit is equal to Show Answer

Q27) A power transmission line feeds input power at 2300 V to a step down transformer with its primary windings having 4000 turns. The number of turns in the secondary in order to get output at 230 V is Show Answer

Q28) In a LCR series circuit, at resonant frequency Show Answer

Q29) A choke is a : Show Answer

Q30) In an ideal parallel LC circuit, the capacitor is charged by connecting it to a dc source which is then disconnected. The current in the circuit Show Answer

Q31) In an oscillating LC circuit the maximum charge on the capacitor is Q. The charge on the capacitor when the energy stored in capacitor is twice that stored in magnetic field, is Show Answer

Q32) A resistance of 40 ohm and an inductance of 95.5 millihenry are connected in series in a 50 cycle / second AC circuit. The impedance of this combination is very nearly Show Answer

Q33) Alternating current can not be measured by DC ammeter because Show Answer

Q34) If L and R denote inductance and resistance respectively which of the following has the dimensions of frequency ? Show Answer

Q35) The average value of alternating current over one complete cycle is Show Answer

Q36) A coil of inductance 40 henry is connected in series with a resistance of 8 ohm and the combination is joined to the terminals of a 2 volt battery. The time constant of the circuit is Show Answer

Q37) A step-down transformer is employed to reduce the main supply of 220 V to 11 V. The primary draws 5 A of current and the secondary draws 90 A. The efficiency of the transformer is Show Answer

Q38) The resonant frequency of a circuit is f. If the capacitance is made 4 times the initial value, then the resonant frequency will become Show Answer

Q39) Large transformers, when used for sometime, become hot and are cooled by circulating oil. The heating of transformer is due to Show Answer

Q40) There is a current of 10 milliampere through an ideal choke coil when connected to 220 volt, 50 hertz supply. The power consumed is Show Answer

Q41) A device which converts electrical energy into mechanical energy is Show Answer

Q42) Energy is stored in the choke coil in the form of Show Answer

Q43) In a step-up transformer, the turns ration is 1 : 2. A Leclanche cell ( emf 1.5 V ) is connected across the primary. The voltage across the secondary is Show Answer

Q44) In a transformer, the number of turns of primary coil and secondary coil are 5 and 4 respectively. If 220 V is applied on the primary coil, then the ratio of primary current to the secondary current is Show Answer

Q45) The power factor in an AC series L-R circuit is Show Answer

Q46) 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 is Show Answer

Q47) The reactance of a coil, when used in the domestic AC power supply ( 220 volt, 50 cycles per second ) is 50 ohm. The inductance of the coil is nearly Show Answer

Q48) An inductor, a capacitor and a resistor are connected in series to an AC supply. When measured with an AC voltmeter, the potential difference across the inductor, capacitor and resistor are respectively 90 volt, 60 volt and 40 volt. Then the supply voltage is Show Answer

Q49) In a series resonant circuit, the AC voltages across resistance R, inductance L and capacitance C are 5 V , 10 V, 10 V respectively. The AC voltage applied to the circuit will be Show Answer

Q50) An rms current 0.6 A flows when an inductance of 40 mH is connected to an AC source of 24 V ( rms ). The angular frequency of the source is Show Answer

Q51) An inductor of 2 henry and a resistance of 10 ohm are connected in series with a battery of 5 volt. The initial rate of change of current is Show Answer

Q52) An alternating current having peak value 14 A used to heat a metal wire. To produce the same heating effect, a constant current i can be used where i is Show Answer

Q53) A dyanmo dissipates 20 watt when it supplies a current of 4 A through it. If the terminal potential difference is 220 volt, then the emf produced is Show Answer

Q54) An ideally efficient transformer has a primary power input of 10 k W. The secondary current when the transformer is on load is 25 ampere. If the primary : secondary turns ratio is 8 : 1, then the potential difference applied to the primary coil is Show Answer

Q55) Lenz's law is a consequence of the law of conservation of : Show Answer

Q56) "The induced e.m.f. is always in such a direction so as to oppose the change that causes it" is called : Show Answer

Q57) An electron moves in the line from left to right, which lies below in the plane of a circular loop of a wire (conductor). What is the direction of current induced, if any, in the loop ? Show Answer

Q58) A coil is wound on a transformer of rectangular cross-section. If all the linear dimensions of the transformer are increased by a factor 2 and number of turns per unit length of the coil remains the same, the self-induction increases by a factor of : Show Answer

Q59) A magnet is taken towards a coil and is moved (i) quickly (ii) slowly, then the induced e.m.f. is : Show Answer

Q60) In a step-up transformer : Show Answer

Q61) In a step-down transformer : Show Answer

Q62) A small transformer does not : Show Answer

Q63) A transformer has no : Show Answer

Q64) Maximum efficiency of a transformer depends : Show Answer

Q65) Auto transformer : Show Answer

Q66) Transmission of electricity is done : Show Answer

Q67) Induction furnaces work on the principle of : Show Answer

Q68) Induction motor for A.C. devices works on the principal of : Show Answer

Q69) Eddy currents do not cause : Show Answer

Q70) The role of self-inductance in a circuit is equivalent to : Show Answer

Q71) In a dead-beat galvanometer the coil is wound over a frame made of : Show Answer

Q72) A transformer has an efficiency of 80%. It works at 4 kilowatt and 100 volt. If the secondary voltage is 240 volt, then the primary and secondary currents are : Show Answer

Q73) The e.m.f. induced between the ends of an axle 1.75 meter long of a railway carriage tavelling on a level ground with a uniform speed of 54 kilometers per hour is ( vertical component of earth's field is 0.5 gauss ): Show Answer

Q74) In case of ideal step-down transformer : Show Answer

Q75) A metallic ring is attached to the wall of a room. When the north pole of a magnet is brought near the ring, the induced current in the ring is : Show Answer

Q76) Two pure inductors each of self inductance L are connected in parallel but are will separated from each other, the total inductance is : Show Answer

Q77) The back e.m.f. in a D.C. motor is maximum when the : Show Answer

Q78) Armature current in D.C. motor is maximum when the motor has : Show Answer

Q79) A bar magnet is dropped along the axis of a copper ring held horizontally. The acceleration of fall is : Show Answer

Q80) An induced e.m.f is produced when a magnet is introduced in a coil. The magnitude of this induced e.m.f. does not depend upon : Show Answer

Q81) In the electromagnetic induction, the induced e.m.f. in independent of Show Answer

Q82) Self inductance of a straight conductor is : Show Answer

Q83) If no. of turns per unit length in a solenoid is tripled, the self inductance of solenoid will Show Answer

Q84) The inductor may store energy : Show Answer

Q85) When a wire loop is rotated in a magnetic field, the direction of induced e.m.f. changes once in : Show Answer

Q86) The minimum value of inductance which can be obtained using three inductances of values 2H, 3H AND 6H is : Show Answer

Q87) If the angular speed of rotation of an armature of alternator is doubled then induced e.m.f. will be : Show Answer

Q88) The current is flowing in two co-axial coils in the same direction. On increasing the distance between the two coils, the electric current will : Show Answer

Q89) Two different loops are concentric and lie in the same plane. The current in the outer loop is clockwise and increasing with time. The induced current in the inner loop is then : Show Answer

Q90) A transformer changes : Show Answer

Q91) A copper disc of radius R is rotated about its center with frequency v in a uniform field of strength B Tesla perpendicular to its plane. The e.m.f. induced between its axle and tip of edge is : Show Answer

Q92) An electric bulb in series with a large inductor when connected across a D.C. source takes a little time before reaching a stable glow. If an iron core is inserted into the inductor the delay will Show Answer

Q93) An electric bulb of 100W is connected in parallel with an ideal inductor of 1H. The arrangement is connected to a 90 V battery through a switch. On pressing the switch. Show Answer

Q94) A wheel with 8 spokes is rotated in a plane normal to the earth's magnetic field so that an e.m.f. of 4 m V is induced between the axle and the rim of the wheel. Keeping all the other things unchanged, the number of spokes is increased to 16. Now the e.m.f. between the axle and rim of the wheel is Show Answer

Q95) A conductor having no ohmic resistance resists the flow of changing current because Show Answer

Q96) A coil of resistance R and inductance L is connected to a battery of E volts e.m.f. The current in the coil is Show Answer

Q97) A copper ring is having a cut. A bar magnet is dropped through the ring with its length along the axis of the ring. Then the acceleration of the falling magnet is Show Answer

Q98) The induced charge in an inductance is independent of : Show Answer

Q99) If the magnetic flux linked with a coil through which a current X A is flowing is Y Wb, then coefficient of self induction is : Show Answer

Q100) A small loop of wire of side (l) is placed inside a large square loop of wire of side (L) (L > > l). The loops are coplanar and their centers coincide. The mutual induction of the system is proportional to Show Answer

Q101) Quantity that remains unchanged in a transformer is Show Answer

Q102) The direction of induced current is such that it opposes the very cause that produces it. This is the law of Show Answer

Q103) The unit of inductance is equivalent to Show Answer

Q104) A long metallic rod (horizontal) with length along the east west direction is falling freely under gravity. The potential difference between its ends will Show Answer

Q105) A Cu-ring is suspended by a thread in a vertical plane. The north pole of a magnet is moved horizontally towards the ring along the axis of the ring. The ring will Show Answer

Q106) A disc of 10.0 cm diameter is rotated at a speed of 3600 r.p.m. inside a long solenoid of 1200 turns per meter on the axis of the solenoid and perpendicular to the plane of the disc. When a current of 1.5 A is passed through the solenoid, the difference in the potential between the axis and circumference of the disc is nearly Show Answer

Q107) A.C. which we use in houses has peak value of nearly : Show Answer

Q108) When two mutually perpendicular alternating magnetic fields superimpose on each other, the resulting field is : Show Answer

Q109) In a D.C. motors, the current flowing through the armature is minimum when induced e.m.f. is : Show Answer

Q110) For 100% efficiency of D.C. motor, the applied potential should be : Show Answer

Q111) The approximate formula expressing the mutual inductance of two thin co-axial loops of the same radius 'a' when their centres are separated by a distance l, with l > > a is : Show Answer

Q112) Find the inductance of a solenoid of length l whose winding is made of copper wire of mass m. The winding resistance is equal to R. The solenoid diameter is considerably less than its length. Show Answer

Q113) In an A.C. circuit, at resonance the phase difference between current and voltage is : Show Answer

Q114) At resonance the power factor of L-C-R circuit is : Show Answer

Q115) The power factor in a circuit connected at a A.C. power supply has a value which is : Show Answer

Q116) Using an A.C. voltmeter the potential difference in the electrical line in a house is read to be 234 volts. If the line frequency is known to be 50 cycles/seconds, the equation for the line voltage V is : Show Answer

Q117) Ohm's law expressed as E= IR Show Answer

Q118) The speed of fan is reduced by putting a rheostat in series with the fan, we consume: Show Answer

Q119) A choke and capacitor are connected in series and current is maximum when input frequency is f. If they are put in parallel, the current is maximum at frequency : Show Answer

Q120) In L-C-R circuit, the value of capacitance is doubled. For the resonant frequency to remain the same, the inductance should be changed from L to : Show Answer

Q121) 220 V a.c. is more dangerous than 220 V d.c. because : Show Answer

Q122) L and R denote inductance and resistance. The dimensions of L/R is : Show Answer

Q123) The time taken for a current to attain the maximum value in d.c. circuit containing 'L' and R depends upon : Show Answer

Q124) An L-C-R circuit is connected to source a.c. At resonance , the phase difference between voltage and current in the circuit is : Show Answer

Q125) Two cables of copper are of equal lengths. One of them has single wire of area A an the other has 10 wires each of cross-section A/10 each. Given their suitability for transporting a.c. and d.c. Show Answer

Q126) A choke coil may be used as a resistance in : Show Answer

Q127) The current in the a.c. circuit measures 5 A. Its maximum instantaneous magnitude will be : Show Answer

Q128) The parallel L-C circuit acts as a simple harmonic oscillator due to exchange of : Show Answer

Q129) In series L-C-R circuit at resonance, the voltage across the inductance is : Show Answer

Q130) A lamp which can carry a current of 10 A at 15 V is connected to an a.c. source of 220 V, 50 Hz, the inductance of choke coil needed to light the lamp is : Show Answer

Q131) An altering current in series LCR circuits is maximum if: Show Answer

Q132) Same current flowing in two a.c. circuits. The first contains only inductance and second contains only capacitance. If the frequency of e.m.f. of a.c. is increased for both, the effect on the current will be : Show Answer

Q133) The value of form factor for altering current is : Show Answer

Q134) With fluorescent tube in A.C. circuit, we connect: Show Answer

Q135) A 220 volt input is supplied to a transformer. The output circuit draws a current of 2.0 ampere at 440 volt. If the efficiency of the transformer is 80% , the current drawn by the primary windings of the transformer is : Show Answer

Q136) A real capacitor can be represented in terms of ideal components as: Show Answer

Q137) A real inductor can be represented as : Show Answer

Q138) An a.c. virtual voltage of 100 virtual volts is applied to a circuit of resistance of 0.5 ohm and inductance 0.01 H, the frequency being 50 Hz. The lag in time in voltage and current is : Show Answer

Q139) When we touch the terminal of a high voltage capacitor, even after a high voltage has been cut off. Then the capacitor has the tendency to : Show Answer

Q140) The number of turns in the primary coil of a transformer is 200 and the number of turns in the secondary coil 10. If 240 volt A.C. is applied to the primary, the output from the secondary will be : Show Answer

Q141) The coil of a choke in a circuit : Show Answer

Q142) The reactance of coil when used in the A.C. power supply ( 220 volt, 50 cycles /s) is 50 ohms. The inductance of the coil is nearly : Show Answer

Q143) Impedance of circuit when a resistance R and a inductor of inductance L are connected in series in an A.C.circuit of frequency v, is : Show Answer

Q144) The ratio of the induced e.m.f. in a coil having 50 turns and rotating with 50 Hz to that of the induced e.m.f. in a coil having 100 turns and rotating with 150 Hz in the same magnetic field is : Show Answer

Q145) 220 V, 50Hz A.C. source is connected to inductance of 0.2 H and a resistance of 20 ohm in series. What is the current in the circuit : Show Answer

Q146) A Lechlanche Cell of e.m.f. 1.4 V is connected to the primary of a tranformer of turn ratio 10:1. The output voltage is : Show Answer

Q147) The coefficient of self inductance of a coil is given by : Show Answer

Q148) A transformer is used to light 140 watt, 24 volt lamp from 240 volts A.C. mains. If the current in the mains is 0.7 A, then the efficiency of transformer is : Show Answer

Q149) Which of the following is correct ? Show Answer

Q150) A short-circuited coil is placed in a time varying magnetic field. Electrical power is dissipated due to to the current induced in the coil. If no. of turns were to be quadrupled and the wire radius halved, the electrical power dissipated would be : Show Answer

Q151) In an ideal parallel LC-circuit, the capacitor is charged by connecting it to a d.c. source which is then disconnected. The current in the circuit : Show Answer

Q152) Electric fan works on the principle of : Show Answer

Q153) A horizontal straight conductor when placed along south north direction falls under gravity there is : Show Answer

Q154) The r.m.s. value of an A.C. of 50 Hz is 10 A. The time taken by an alternating current in reaching from zero to maximum value and the peak value will be : Show Answer

Q155) In a LCR series circuit, at resonant frequency : Show Answer

Q156) Eddy currents are produced in : Show Answer

Q157) Which law follows the law of conservation of energy ? Show Answer

Q158) A lamp of same rating is used to a 200 V d.c. and a 200 V a.c. supply. The lamp will : Show Answer

Q159) In an induction coil, the coefficient of mutual inductance is 4 henry. If a current of 5 A in the primary coil is cut off in 1/1500s, the e.m.f. at the terminals of the secondary coil will be: Show Answer

Q160) The self inductance of a solenoid of length L, the area of cross section A and having N turns is : Show Answer

Q161) A e.m.f. of 100 millivolt is induced in a coil when the current in another nearby coil becomes 10 A from zero in 0.1 second. The coefficient of mutual induction between the two coils will be ? Show Answer

Q162) A 100 mH coil carries a current of 10 A. The magnetic energy stored in the coil is Show Answer

Q163) The capacitance is made 1/4th in an LCR circuit, then how much should the inductance be changed so that the circuit remains in resonance : Show Answer

Q164) The ratio of turns of transformer is 2:3. Given that the current through the primary is 3 A, then what is the current through the load resistance : Show Answer

Q165) What is the equivalent inductance of a system of two inductors L joined in parallel : Show Answer

Q166) One henry is equal to Show Answer

Q167) A transformer with efficiency 80% works at 4 kW and 100 V. If the secondary voltage is 200 V, then the primary and secondary currents are respectively : Show Answer

Q168) A metallic ring is dropped down, keeping its plane perpendicular to a constant and horizontal magnetic field. The ring enters the region of magnetic field at t = 0 and completely emerges out at t = T sec. The current in the ring varies as : Show Answer

Q169) Two coil of self inductances 2 mH and 8 mH are placed so close together that the effective flux in one coil is completely linked with the other. The mutual inductance between those coils is : Show Answer

Q170) The core of a transformer is laminated because: Show Answer

Q171) A transformer is used to light a 100 W and 110 V lamp from a 220 V mains. If the main current is 0.5 amp, the efficiency of the transformer is approximately : Show Answer

Q172) A conducting circular loop is placed in a uniform magnetic field 0.04 T with its plane perpendicular to the magnetic field. The radius of the loop starts shrinking at 2 mm /s. The induced e.m.f. in the loop when the radius is 2 cm is : Show Answer

Q173) A loss free transformer has 500 turns in the primary and 2500 in secondary. The meters of the secondary are indicating 200 volts, 18 ampere. Under these conditions, what would be the meters of the primary read ? Show Answer

Q174) If applied voltage on a motor is 200 volt and back e.m.f is 100 volt the efficiency of the motor is Show Answer

Q175) It is desired to send an altering current 5 sin 400 t through a solenoid that has a self inductance of 3 mH. If the resistance of the solenoid is assumed to be negligible, the voltage impressed across the solenoid terminals to provide this current is : Show Answer

Q176) With the increase in frequency of an a.c. supply, the impedance of an L-C-R series circuit Show Answer

Q177) An artificial satellite with a metal surface is moving about the earth in a circular orbit. A current will be induced in the satellite if Show Answer

Q178) A conducting rod is moving with velocity v in a magnetic field B. An induced e.m.f. will be generated between its two ends if Show Answer

Q179) The coefficient of self-induction of two coils are 0.01 H and 0.03 H respectively. If they oppose each other then the resultant self induction will be, if M = 0.01 H Show Answer

Q180) A current time curve is shown in the following diagram. This type of current is passed in the primary coil of a transformer. The nature of induced e.m.f. in the secondary coil will be : Show Answer

Q181) The dimensions of the quantity L/CVR are equivalent to those of : Show Answer

Q182) A cycle wheel with 64 spokes is rotating with N rotations per second at right angles to horizontal component of magnetic field. The induced e.m.f. generated between its axle and rim is E. If the number of spokes is reduced to 32 then the value of induced e.m.f. will be : Show Answer

Q183) Same current is flowing in two identical coaxial circular coils. On looking the coils from a point at the center between them, the current in one coil appears to be flowing in clockwise direction. If the two coils are displaced towards each other then the value of current Show Answer

Q184) The phase difference between the flux linked with a coil rotating in a uniform magnetic field and induced e.m.f. produced in it is Show Answer

Q185) If the capacity of a condenser is 1 farad then its resistance in a D.C. circuit will be Show Answer

Q186) The values of alternating current and alternating e.m.f. for a resistance less choke coil are 1 A and 220 volt respectively. The power loss in the circuit will be : Show Answer

Q187) A bulb and a condenser are connected in series with an A.C. source. On increasing the frequency of the source its brightness will : Show Answer

Q188) The constant speed of the frame is Show Answer

Q189) The emf induced in the loop is Show Answer

Q190) The potential difference between the points a and b is equal to Show Answer

Q191) Statement 1 : A short cylindrical bar magnet is dropped down a vertical aluminium pipe of slightly larger diameter, and of length several meters. It takes several seconds to emerge at the bottom, whereas an unmagnetized iron takes a fraction of a second.
Statement 2 : Eddy currents are generated in aluminium pipe which dampen the motion of bar magnet
Show Answer

Q192) Statement 1 : Magnetic flux is a vector quantity.
Statement 2 : Value of magnetic flux can be positive, negative or zero Show Answer

Q193) Which of the following represents the current generated by the apparatus Show Answer

Q194) An increase in which of the following parameters would not increase the current generated by the apparatus, Show Answer

Q195) What will be the direction of current in the apparatus shown ? Show Answer

Q196) Statement 1 : Induced e.m.f in an inductor may be non-zero, even if the current through it is zero.
Statement 2 : For alternating sinusoidal current passing through an inductor, voltage across inductor and current are completely out of phase.
Show Answer

Q197) The voltage drop across the resistor is given as Show Answer

Q198) The resistance of the coil is Show Answer

Q199) The voltage drop across the coil is Show Answer

Q200) Statement 1 : A resistance is connected to an A.C. source. Now a capacitor is included in series. The average power absorbed by the resistance will remain same.
Statement 2 : Capacitor does not consume power.
Show Answer

Q201) The device X can be Show Answer

Q202) Let the two devices have same resistance. The voltage across the series combination is V an current is i. Select the current alternative Show Answer

Q203) The device Y cannot be Show Answer

Q204) We cannot use a D. C. Voltmeter to measure an alternating voltage because, Show Answer

Q205) The time taken by an A.C. of frequency 50 Hz to reach from 0 to positive maximum is Show Answer

Q206) The electric supply line in houses works on 220 V. The amplitude of e.m.f. will be Show Answer

Q207) In an A.C. circuit the peak value of voltage is 424 V. Its effective voltage is Show Answer

Q208) An electric bulb is designed to operate at 12 V D.C.. If it is connected to A.C, it gives the same brightness. Then the peak value of the A.C. voltage is Show Answer

Q209) If the effective value of A.C. in a circuit is 10 A, then the peak value of the current is Show Answer

Q210) If the frequency in an A.C. circuit is 100 Hz, then the time taken by the voltage to cover from positive maximum to next positive maximum will be Show Answer

Q211) The rms value of a sinusoidal ac current is equal to its instantaneous value at an angle of ______________ degree. Show Answer

Q212) What is the frequency of an ac signal having a time period of 50 nanosecond? Show Answer

Q213) The length of each side of a square coil of 10 turns is 10 cm. This coil rotates in a magnetic field of induction 0.02 Tesla. If the maximum induced e.m.f. in the coil is 20 mV, then the angular velocity of the coil will be Show Answer

Q214) The a. c. main supply is given to be 220 V. What would be the average e.m.f. during a positive half cycle? Show Answer

Q215) The peak value of an alternating e.m.f. is 141.4 V. What would be the reading of an a. c. voltmeter when connected across this e.m.f.? Show Answer

Q216) The household supply voltage as measured by an a. c. voltmeter is 220 volts. If the frequency of a. c. supply is 50 Hz, then the equation of the line voltage, will be Show Answer

Q217) The domestic power supply of 220 V, 50 Hz is connected to a resistor. What is the time taken by the alternating current flowing in the resistor, to change from its maximum value to rms value? Show Answer

Q218) An a. c. ammeter is used to measure the current in a circuit. When a d. c. current passes through the circuit, the a. c. ammeter reads 3 A. But when an a. c. current is passed through the circuit, the a. c. ammeter reads 4 A. What will be the reading of the a. c. ammeter, when the same DC and AC are allowed to flow through the circuit simultaneously? Show Answer

Q219) A current of 6 A flows through a coil when connected to a 24 volt d.c. supply. To get the same current with a 50 Hz a.c. supply, the voltage required is 30 V. What is the power factor of the coil? Show Answer

Q220) If a dry cell of e.m.f. 1.5 V is applied to a capacitor, the reactance of the capacitor will be Show Answer

Q221) When a capacitance is connected in series with a series L-R, a.c. circuit, the total impedance of the circuit Show Answer

Q222) An electric bulb consumes only 25% of the peak power in an a.c. circuit. What is the phase difference between the circuit current and the applied a.c. voltage? Show Answer

Q223) In a circuit containing an inductance of zero resistance, the current leads the applied a.c. voltage by a phase angle of Show Answer

Q224) What is the phase difference between the virtual current and al voltage when the current in the circuit is wattless? Show Answer

Q225) The ohm second is equal to Show Answer

Q226) When an alternating voltage of 100 V, 50 Hz is applied to a choke coil, it takes a current of 10 A and the power is 500 W. What is the reactance of the choke coil? Show Answer

Q227) A choke is preferred to a resistance for limiting the current in an a.c. circuit because Show Answer

Q228) In an AC circuit, the reactance is equal to the resistance. What is the power factor of the circuit? Show Answer

Q229) Same current is flowing in two alternating circuits. The first circuit contains only inductance and the other contains only a capacitor. What is the effect on the values of the current in the two circuits, if the frequency the alternating e.m.f. is increased? Show Answer

Q230) A capacitor has capacity C and reactance X. If the capacitance and frequency are doubled, the reactance will be Show Answer

Q231) When a coil is connected to a Leclanche cell, its resistance is found to be R. What is the effect on its resistance, if it is connected to an a.c. source? Show Answer

Q232) The average power dissipated in an A.C. circuit containing resistance, inductance and capacitance depends upon Show Answer

Q233) An inductor of inductance L and a resistor of resistance R are joined in series and connected to an a.c. source of frequency w. What is the power dissipated in the circuit? Show Answer

Q234) An alternating e.m.f. of angular frequency omega is applied across an inductance. The instantaneous power developed in the circuit has an angular frequency Show Answer

Q235) The self inductance of the motor of an electric fan is 10 H. In order to impart maximum power at 50 Hz, it should be connected to a capacitance of Show Answer

Q236) An alternating e.m.f. is applied to a series L-C-R circuit. If the frequency of the applied e.m.f. is more than the resonant frequency of the circuit then the circuit will act as Show Answer

Q237) For a series L-C-R circuit the power loss at resonance is Show Answer

Q238) The resonant frequency of a circuit is 100 Hz. If the capacitor is replaced by another capacitor of capacity = 4 times the original capacity, then the resonant frequency will be Show Answer

Q239) An LCR Circuit is in resonance. The capacitance is decreased to 1/4 of its original value. What should be the new inductance so that the circuit remains in resonance? Show Answer

Q240) Out of the many input signals of different frequencies, a series resonant circuit will accept one which has Show Answer

Q241) A parallel resonant circuit can be used Show Answer

Q242) In a series L-C-R circuit, the values of L and C are so adjusted that the maximum current flows through the circuit. In this case, if the P.D. across L is 200 V, then the P.D. across the capacitance will be Show Answer

Q243) In a series LCR circuit, at resonant frequency, Show Answer

Q244) Which is the wrong relation from the following? At resonance, in a series L-C-R a.c. circuit Show Answer

Q245) The square root of the product of inductance and capacitance has the dimensions of Show Answer

Q246) When there is resonance in an a.c. circuit containing L, C and R, the current Show Answer

Q247) An acceptor circuit is Show Answer

Q248) In LCR series circuit if the frequency is increased, the impedance of the circuit Show Answer

Q249) In series LCR circuit at resonance, the power factor is Show Answer

Q250) In an LCR series circuit, the voltage across each of the components L, C and R is 20 V. The voltage across the L-C combination will be Show Answer

Q251) L, C and R represent the physical quantities inductance, capacitance and resistance respectively. Which one of the following combination will have the dimensions of frequency? Show Answer

Q252) In series LCR resonant circuit the voltage across the resistance, capacitance and inductance is 10 V each. The by capacitance is then removed. What is the voltage across the inductance? Show Answer

Q253) Which one of the following combinations should be selected for better tuning of an L-C-R circuit used for communication? Show Answer

Q254) In an LCR series a.c. circuit, the voltage across each of the components L, C and R is 60 V. What is the voltage across the LC combination? Show Answer

Q255) In an oscillating LC circuit the maximum charge on the capacitor is Q. What is the charge on the capacitor when the energy is stored equally between the electric and magnetic fields? Show Answer

Q256) The LC parallel resonant circuit Show Answer