The resistance of a coil for dc is in ohms. In ac, the resistance
If instantaneous current is given by i = 4 cos ( ω t + φ ) amperes, then the r.m.s. value of current is
A generator produces a voltage that is given by V = 240 sin 120 t , where t is in seconds. The frequency and r.m.s. voltage are
In an ac circuit, peak value of voltage is 423 volts. Its effective voltage is
The peak value of an Alternating current is 6 amp, then r.m.s. value of current will be
The voltage of an ac supply varies with time (t) as V = 120 sin 100 π tcos 100 π t . The maximum voltage and frequency respectively are
An LCR series circuit with a resistance of 100 ohm is connected to an ac source of 200 V (r.m.s.) and angular frequency 300 rad/s. When only the capacitor is removed, the current lags behind the voltage by 60 o . When only the inductor is removed the current leads the voltage by 60 o . The average power dissipated is
In a series circuit C = 2 μF , L = 1 mH and R = 10 Ω , when the current in the circuit is maximum, at that time the ratio of the energies stored in the capacitor and the inductor will be
Which one of the following curves represents the variation of impedance (Z) with frequency f in series LCR circuit
The variation of the instantaneous current (I) and the instantaneous emf (E) in a circuit is as shown in fig. Which of the following statements is correct
The current ‘i’ in an inductance coil varies with time ‘t’ according to following graph Which one of the following plot shows the variations of voltage in the coil
In an LCR circuit R=100 ohm. When capacitance C is removed, the current lags behind the voltage by π / 3 . When inductance L is removed, the current leads the voltage by π / 3 . The impedance of the circuit is
The voltage across a pure inductor is represented by the following diagram. Which one of the following diagrams will represent the current
If A and B are identical bulbs which bulbs glows brighter
The phase difference between the voltage and the current in an ac circuit is π / 4 . If the frequency is 50 Hz then this phase difference will be equivalent to a time of
A capacitor is fully charged with a battery. Then the battery is removed and coil is connected with the capacitor in parallel, current varies as
The square root of the product of inductance and capacitance has the dimension of
A transformer is employed to
In a transformer 220 ac voltage is increased to 2200 volts. If the number of turns in the secondary are 2000, then the number of turns in the primary will be
The alternating voltage induced in the secondary coil of a transformer is mainly due to
A transformer is employed to reduce 220 V to 11 V. The primary draws a current of 5 A and the secondary 90 A. The efficiency of the transformer is
A 100% efficient transformer has 100 turns in the primary and 25 turns in its secondary coil. If the current in the secondary coil is 4 amp, then the current in the primary coil is
A power transformer is used to step up an alternating e.m.f. of 220 V to 11 kV to transmit 4.4 kW of power. If the primary coil has 1000 turns, what is the current rating of the secondary ? Assume 100% efficiency for the transformer
In a transformer the primary has 500 turns and secondary has 50 turns. 100 volts are applied to the primary coil, the voltage developed in the secondary will be
In a step up transformer, 220 V is converted into 2200 V. The number of turns in primary coil is 600. What is the number of turns in the secondary coil
A step-up transformer operates on a 230 V line and supplies a load of 2 ampere. The ratio of the primary and secondary windings is 1 : 25. The current in the primary is
Large transformers, when used for some time, become hot and are cooled by circulating oil. The heating of transformer is due to
In a transformer, number of turns in the primary are 140 and that in the secondary are 280. If current in primary is 4A then that in the secondary is
In a step up transformer, if ratio of turns of primary to secondary is 1 : 10 and primary voltage is 230 V. If the load current is 2A, then the current in primary is
The turn ratio of a transformers is given as 2 : 3. If the current through the primary coil is 3 A, thus calculate the current through load resistance
Core of transformer is made up of
A step-down transformer is used on a 1000 V line to deliver 20 A at 120 V at the secondary coil. If the efficiency of the transformer is 80% the current drawn from the line is .
In L C circuit the inductance L = 40 mH and capacitance C = 100 μ F . If a voltage V t = 10 sin 314 t is applied to the circuit, the current in the circuit is given as
An inductance coil has a reactance of 100 Ω . When an AC signal of frequency 1000 Hz is applied to the coil, the applied voltage leads the current by 45 0 . The self-inductance of the coil is:
In the given figure, which voltmeter will read zero voltage at resonant frequency ω
The frequency of oscillation of current in the inductance is
The potential difference V and the current i flowing through an instrument in an ac circuit of frequency f are given by V = 5 cosω t volts and I = 2 sin ω t amperes (where ω = 2 πf ). The power dissipated in the instrument is
In an ac circuit I = 100 sin 200 π t. The time required for the current to achieve its peak value will be
A sinusoidal ac current flows through a resistor of resistance R. If the peak current is I p , then the power dissipated is
The peak value of 220 volts of ac mains is
A 40 Ω electric heater is connected to a 200 V, 50 Hz mains supply. The peak value of electric current flowing in the circuit is approximately
In the circuit shown in the figure, the ac source gives a voltage V = 20 cos ( 2000 t ) . Neglecting source resistance, the voltmeter and ammeter reading will be
In a certain circuit current changes with time according to i = 2 t . r.m.s. value of current between t = 2 to t = 4 s will be
Match the following Currents r.m.s. values (a) x 0 sinω t (i) x 0 (b) x 0 sinω tcosω t (ii) x 0 2 (c) x 0 sinω t + x 0 cosω t (iii) x 0 ( 2 2 ) (a) (b) (c) (1) i ii iii (2) ii iii i (3) i iii ii (4) iii i ii
A virtual current of 4A and 50 Hz flows in an ac circuit containing a coil. The power consumed in the coil is 240 W. If the virtual voltage across the coil is 100 V its inductance will be
In the adjoining ac circuit the voltmeter whose reading will be zero at resonance is
For a series RLC circuit R = X L = 2X C . The impedance of the circuit and phase difference (between) V and i will be
An ac source of variable frequency f is connected to an LCR series circuit. Which one of the graphs in figure. represents the variation of current of current I in the circuit with frequency f
Which of the following curves correctly represents the variation of capacitive reactance X C with frequency f
The instantaneous values of current and voltage in an ac circuit are i = 100 sin 314 t amp and e = 200 sin ( 314 t + π / 3 ) V respectively. If the resistance is 1 Ω then the reactance of the circuit will be
The transformation ratio in the step-up transformer is
We can reduce eddy currents in the core of transformer
In a lossless transformer an alternating current of 2 amp is flowing in the primary coil. The number of turns in the primary and secondary coils are 100 and 20 respectively. The value of the current in the secondary coil is
The coils of a step down transformer have 500 and 5000 turns. In the primary coil an ac of 4 ampere at 2200 volts is sent. The value of the current and potential difference in the secondary coil will be
A step-up transformer has transformation ratio of 3 : 2. What is the voltage in secondary if voltage in primary is 30 V
A transformer has 100 turns in the primary coil and carries 8 A current. If input power is one kilowatt, the number of turns required in the secondary coil to have 500V output will be
A step up transformer has transformation ration 5 : 3. What is voltage in secondary if voltage in primary is 60 V
The output voltage of a transformer connected to 220 volt line is 1100 volt at 2 amp current. Its efficiency is 100%. The current coming from the line is
In an inductor of inductance L = 100 mH, a current of I=10 A is flowing. The energy stored in the inductor is
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
A LCR circuit behaves like a damped harmonic oscillator. Comparing it with a physical spring mass damped oscillator having damping constant ‘b’, the correct equivalence would be
A 750 Hz, 20 V (rms) source is connected to a resistance of 100 Ω , an inductance of 0.1803 H and a capacitance of 10 μ F all in series. The time in which the resistance (heat capacity 2 J/ºC) will get heated by 10ºC. (assume no loss of heat to the surroundings) is close to :
If a direct current of “a” ampere is super imposed on an alternating current I = b sin ω t flowing through a wire, what is the effective value of resulting current in the circuit
In an LC circuit shown in figure, C = 1F, L = 4H. At time t = 0, charge in the capacitor is 4C and it is decreasing at the rate of 5 Cs − 1 . Choose the correct statement.
The natural angular frequency of the circuit shown in figure is
In the following electrical network at t < 0 (figure), key is placed on (1) till the capacitor got fully charged. Key is placed on (2) at t = 0. Time when the energy in both the capacitor and the inductor will be same for the first time is
The rms value of alternating current i = 2 sin 100 π t + 2 cos 100 π t + 30 0 is (in ampere)
Two identical incandescent light bulbs are connected as shown in the figure. When the circuit is connected to an AC voltage source of frequency f , which of the following observations will be correct?
If L = 25 mH, C=1mF and R = 10 Ω then R.M.S current across source is
As given in the figure, a series circuit connected across a 200 V, 60 Hz line consists of a capacitor of capacitive reactance 30ohm , a non-inductive resistor of 44 ohm , and a coil of inductive reactance 90ohm and resistance 36ohm . The power dissipated in the coil is (watt)
The power is transmitted from a power house on high voltage ac because
Alternating current can not be measured by dc ammeter because
In an ac circuit, V and I are given by V = 100 sin (100 t) volts, I = 100 sin 100 t + π 3 mA . The power dissipated in circuit is
If E 0 represents the peak value of the voltage in an ac circuit, the r.m.s. value of the voltage will be
The frequency of ac mains in India is
The r.m.s. value of an ac of 50 Hz is 10 amp. The time taken by the alternating current in reaching from zero to maximum value and the peak value of current will be
The root mean square value of the alternating current is equal to
The peak value of an alternating e.m.f. E is given by E = E 0 cosω t is 10 volts and its frequency is 50 Hz. At time t = 1 600 sec , the instantaneous e.m.f. is
If a current I given by I 0 sin ω t − π 2 flows in an ac circuit across which an ac potential of E = E 0 sinω t has been applied, then the power consumption P in the circuit will be
An ac generator produced an output voltage E = 170 sin 377 t volts , where t is in seconds. The frequency of ac voltage is
In general in an alternating current circuit
An alternating current is given by the equation i = i 1 cosω t + i 2 sinω t . The r.m.s. current is given by
In an ac circuit, the current is given by i = 5 sin 100 t − π 2 and the ac potential is V = 200 sin ( 100 ) volt . Then the power consumption is
An electric lamp is connected to 220 V, 50 Hz supply. Then the peak value of voltage is
In a circuit, the value of the alternating current is measured by hot wire ammeter as 10 ampere. Its peak value will be
The voltage of domestic ac is 220 volt. What does this represent
The r.m.s. voltage of domestic electricity supply is 220 volt . Electrical appliances should be designed to withstand an instantaneous voltage of
In an ac circuit with voltage V and current I, the power dissipated is
A bulb is connected first with dc and then ac of same voltage then it will shine brightly with
The frequency of an alternating voltage is 50 cycles/sec and its amplitude is 120V. Then the r.m.s. value of voltage is
An ac supply gives 30 V r.m.s. which passes through a 10 Ω resistance. The power dissipated in it is
A resistance of 20 ohms is connected to a source of an alternating potential V = 220 sin ( 100 πt ) . The time taken by the current to change from its peak value to r.m.s value is
Voltage and current in an ac circuit are given by V = 5 sin 100 πt − π 6 and I = 4 sin 100 πt + π 6
An alternating voltage is represented as E = 20 sin 300 t . The average value of voltage over one cycle will be
In an ac circuit, the r.m.s. value of current, I rms is related to the peak current, I 0 by the relation
If an ac main supply is given to be 220 V. What would be the average e.m.f. during a positive half cycle
A 280 ohm electric bulb is connected to 200V electric line. The peak value of current in the bulb will be
The ratio of peak value and r.m.s value of an alternating current is
An ac source is rated at 220V, 50 Hz. The time taken for voltage to change from its peak value to zero is
If the value of potential in an ac circuit is 10V, then the peak value of potential is
If an alternating voltage is represented as E = 141 sin ( 628 t ) , then the rms value of the voltage and the frequency are respectively
Choke coil works on the principle of
The maximum value of a.c. voltage in a circuit is 707V. Its rms value is
A choke coil has
Choke coil is used to control
Current in the circuit is wattless, if
The phase angle between e.m.f. and current in LCR series ac circuit is
A choke coil is preferred to a rheostat in ac circuit as
An alternating e.m.f. is applied to purely capacitive circuit. The phase relation between e.m.f. and current flowing in the circuit is or in a circuit containing capacitance only
An ac source is connected to a resistive circuits. Which of the following is true?
The average power dissipated in a pure inductor of inductance L when an ac current is passing through it, is
An alternating current of frequency ‘ f ‘ is flowing in a circuit containing a resistance R and a choke L in series. The impedance of this circuit is
A resonant ac circuit contains a capacitor of capacitance 10 − 6 F and an inductor of 10 − 4 H . The frequency of electrical oscillations will be
Power delivered by the source of the circuit becomes maximum, when
An alternating voltage is connected in series with a resistance R and an inductance L If the potential drop across the resistance is 200 V and across the inductance is 150 V, then the applied voltage is
An inductive circuit contains resistance of 10 Ω and an inductance of 20 H. If an ac voltage of 120 V and frequency 60 Hz is applied to this circuit, the current would be nearly
Same current is flowing in two alternating circuits. The first circuit contains only inductance and the other contains only a capacitor. If the frequency of the e.m.f. of ac is increased, the effect on the value of the current will be
A capacitor is a perfect insulator for
In a circuit containing an inductance of zero resistance, the e.m.f. of the applied ac voltage leads the current by
In a pure inductive circuit or In an ac circuit containing inductance only, the current
A 20 volts ac is applied to a circuit consisting of a resistance and a coil with negligible resistance. If the voltage across the resistance is 12 V, the voltage across the coil is
A resistance of 300 Ω and an inductance of 1 π henry are connected in series to a ac voltage of 20 volts and 200 Hz frequency. The phase angle between the voltage and current is
The power factor of LCR circuit at resonance is
An inductance of 1 mH a condenser of 10 μ F and a resistance of 50 Ω are connected in series. The reactances of inductor and condensers are same. The reactance of either of them will be
The natural frequency of LC circuit is:
An alternating voltage E = 200 2 sin ( 100 t ) is connected to a 1 microfarad capacitor through an ac ammeter. The reading of the ammeter shall be
An ac circuit consists of an inductor of inductance 0.5 H and a capacitor of capacitance 8 μ F in series. The current in the circuit is maximum when the angular frequency of ac source is
The average power dissipation in a pure capacitance in ac circuit is
In a region of uniform magnetic induction B = 10 − 2 tesla , a circular coil of radius 30 cm and resistance π 2 ohm is rotated about an axis which is perpendicular to the direction of B and which forms a diameter of the coil. If the coil rotates at 200 rpm the amplitude of the alternating current induced in the coil is
An inductive circuit contains a resistance of 10 ohm and an inductance of 2.0 henry. If an ac voltage of 120 volt and frequency of 60 Hz is applied to this circuit, the current (in A) in the circuit would be
In a LCR circuit having L = 8.0 henry, C = 0.5 μ F and R = 100 ohm in series. The resonance frequency in per second is
In LCR circuit, the capacitance is changed from C to 4C. For the same resonant frequency, the inductance should be changed from L to
A 120 volt ac source is connected across a pure inductor of inductance 0.70 henry. If the frequency of the source is 60 Hz, the current passing through the inductor is
The impedance of a circuit consists of 3 ohm resistance and 4 ohm reactance. The power factor of the circuit is
L, C and R denote inductance, capacitance and resistance respectively. Pick out the combination which does not have the dimensions of frequency
The power factor of a good choke coil is
If resistance of 100 Ω , inductance of 0.5 henry and capacitance of 10 × 10 − 6 F are connected in series through 50 Hz ac supply, then impedance is
An alternating current source of frequency 100 Hz is joined to a combination of a resistance, a capacitance and a coil in series. The potential difference across the coil, the resistance and the capacitor is 46, 8 and 40 volt respectively. The electromotive force of alternating current source in volt is
A 10 ohm resistance, 5 mH coil and 10 μ F capacitor are joined in series. When a suitable frequency alternating current source is joined to this combination, the circuit resonates. If the resistance is halved, the resonance frequency
L, C and R represent physical quantities inductance, capacitance and resistance respectively. The combination representing dimension of frequency is
In a series circuit R = 300 Ω , L = 0.9 H, C = 2.0 μ F and ω = 1000 rad/sec. The impedance of the circuit is
In a L-R circuit, the value of L is 0 .4 π henry and the value of R is 30 ohm. If in the circuit, an alternating e.m.f. of 200 volt at 50 cycles per sec is connected, the impedance of the circuit and current will be
The reactance of a coil when used in the domestic ac power supply (220 volt, 50 cycles) is 100 ohm. The self inductance of the coil is nearly
In a series LCR circuit, operated with an ac of angular frequency ω , the total impedance is
The reactance of a 25 μF capacitor at the ac frequency of 4000 Hz is
The frequency for which a 5 μF capacitor has a reactance of 1 1000 ohm is given by
An e.m.f. E = 4 cos ( 1000 t ) volt is applied to an LR-circuit of inductance 3 mH and resistance 4 ohms. The amplitude of current in the circuit is
A coil of inductance L has an inductive reactance of X L in an AC circuit in which the effective current is I. The coil is made from a super-conducting material and has no resistance. The rate at which power is dissipated in the coil is
The phase difference between the current and voltage of LCR circuit in series combination at resonance is
In a series resonant circuit, the ac voltage across resistance R, inductance L and capacitance C are 5 V, 10 V and 10 V respectively. The ac voltage applied to the circuit will be
In an ac circuit, a resistance of R ohm is connected in series with an inductance L. If phase angle between voltage and current be 45°, the value of inductive reactance will be
The coefficient of induction of a choke coil is 0.1 H and resistance is 12 Ω . If it is connected to an alternating current source of frequency 60 Hz, then power factor will be
When 100 volt dc is applied across a coil, a current of 1 amp flows through it. When 100 volt ac at 50 cycle s -1 is applied to the same coil, only 0.5 ampere current flows. The impedance of the coil is
For series LCR circuit, wrong statement is
In a purely resistive ac circuit, the current
A 12 ohm resistor and a 0.21 henry inductor are connected in series to an ac source operating at 20 volts, 50 cycle/second. The phase angle between the current and the source voltage is (tan -1 5.5 = 80 0 approx)
If an 8 Ω resistance and 6 Ω reactance are present in an ac series circuit then the impedance of the circuit will be
What will be the phase difference between virtual voltage and virtual current, when the current in the circuit is wattless
In the non-resonant circuit, what will be the nature of the circuit for frequencies higher than the resonant frequency
The resonant frequency of a circuit is f. If the capacitance is made 4 times the initial values, then the resonant frequency will become
In an ac circuit, the potential difference across an inductance and resistance joined in series are respectively 16 V and 20 V. The total potential difference across the circuit is
A 220 V, 50 Hz ac source is connected to an inductance of 0.2 H and a resistance of 20 ohm in series. What is the current in the circuit
An LCR circuit contains R = 50 Ω , L = 1 mH and C = 0.1 μ F. The impedance of the circuit will be minimum for a frequency of
In a series LCR circuit, resistance R = 10 Ω and the impedance Z = 20 Ω . The phase difference between the current and the voltage is
A series ac circuit consist of an inductor and a capacitor. The inductance and capacitance is respectively 1 henry and 25 μF . If the current is maximum in circuit then angular frequency will be
An alternating e.m.f. of frequency v = 1 2 π LC is applied to a series LCR circuit. For this frequency of the applied e.m.f.
In the circuit shown below, the ac source has voltage V = 20 cos ( ωt ) volts with ω = 2000 rad/sec. the amplitude of the current will be nearest to
The value of the current through an inductance of 1H and of negligible resistance, when connected through an ac source of 200 V and 50 Hz, is
The quality factor of LCR circuit having resistance (R) and inductance (L) at resonance frequency ( ω ) is given by
Power factor is maximum in an LCR circuit when
In an ac circuit the reactance of a coil is 3 times its resistance, the phase difference between the voltage across the coil to the current through the coil will be
In an ac circuit, the current lags behind the voltage by π / 3 . The components in the circuit are
The reactance of a coil when used in the domestic ac power supply (220 volts, 50 cycles per second) is 50 ohms. The inductance of the coil is nearly
A resistance of 40 ohm and an inductance of 95.5 millihenry are connected in series in a 50 cycles/second ac circuit. The impedance of this combination is very nearly
For high frequency, a capacitor offers
The coil of choke in a circuit
In a circuit, the current lags behind the voltage by a phase difference of π / 2 . The circuit contains which of the following
The inductive reactance of an inductor of 1 π henry at 50 Hz frequency is
An oscillator circuit consists of an inductance of 0.5mH and a capacitor of 20 μF . The resonant frequency of the circuit is nearly
Reactance of a capacitor of capacitance C μF for ac frequency 400 π Hz is 25 Ω . The value C is
A circuit has a resistance of 11 Ω , an inductive reactance of 25 Ω and a capacitive resistance of 18 Ω . It is connected to an ac source of 260 V and 50 Hz. The current through the circuit (in amperes) is
The power factor of an ac circuit having resistance (R) and inductance (L) connected in series and an angular velocity ω is
A 0.7 henry inductor is connected across a 120V – 60 Hz ac source. The current in the inductor will be very nearly
There is a 5 Ω resistance in an ac, circuit. Inductance of 0.1H is connected with it in series. If equation of ac e.m.f. is 5 sin 50 t then the phase difference between current and e.m.f. is
An inductor of inductance L and resistor of resistance R are joined in series and connected by a source of frequency ω . Power dissipated in the circuit is
In a ac circuit of capacitance the current from potential is
A coil of 200 Ω resistance and 1.0 H inductance is connected to an ac source of frequency 200 / 2 π Hz . Phase angle between potential and current will be
In a LCR circuit the pd between the terminals of the inductance is 60 V, between the terminals of the capacitor is 30 V and that between the terminals of resistance is 40 V. the supply voltage will be equal to ……
Radio frequency choke uses core of
In a LCR circuit capacitance is changed from C to 2C. For the resonant frequency to remain unchanged, the inductance should be change from L to
In an LCR series ac circuit, the voltage across each of the components L, C and R is 50 V. the voltage across the LC combination will be
A coil has L = 0.04 H and R = 12 Ω . When it is connected to 220 V, 50 Hz supply the current flowing through the coil, in amperes is
The current in series LCR circuit will be maximum when ω is
Which of the following components of a LCR circuit, with ac supply, dissipates energy
An inductor L and a capacitor C are connected in the circuit as shown in the figure. The frequency of the power supply is equal to the resonant frequency of the circuit. Which ammeter will read zero ampere
In a circuit L, C, and R are connected in series with an alternating voltage source of frequency f. The current leads the voltage by 45°. The value of C is
In an A.C. circuit the current
For the series LCR circuit shown in the figure, what is the resonance frequency and the amplitude of the current at the resonating frequency
When 100 volts dc is supplied across a solenoid, a current of 1.0 amperes flows in it. When 100 volts ac is applied across the same coil, the current drops to 0.5 ampere. If the frequency of ac source is 50 Hz, then the impedance and inductance of the solenoid are
In an LR-circuit, the inductive reactance is equal to the resistance R of the circuit. An e.m.f. E = E 0 cos ( ωt ) applied to the circuit. The power consumed in the circuit is
In the circuit shown below, what will be the readings of the voltmeter and ammeter
An alternating e.m.f. of angular frequency ω is applied across an inductance. The instantaneous power developed in the circuit has an angular frequency
In the circuit given below, what will be the reading of the voltmeter
A bulb and a capacitor are connected in series to a source of alternating current. If its frequency is increased, while keeping the voltage of the source constant, then
The diagram shows a capacitor C and a resistor R connected in series to an ac source. V 1 and V 2 are voltmeters and A is an ammeter Consider now the following statements I. Readings in A and V 2 are always in phase II. Reading in V 1 is ahead in phase with reading in V 2 III. Readings in A and V 1 are always in phase which of these statements are/is correct
One 10 V, 60 W bulb is to be connected to 100 V line. The required induction coil has self inductance of value ( f = 50 Hz )
The voltage of an ac source varies with time according to the equation V = 100 sin 100 πtcos 100 πt where t is in seconds and V is in volts. Then
In the circuit shown in figure neglecting source resistance the voltmeter and ammeter reading will respectively, will be
A telephone wire of length 200 km has a capacitance of 0.014 μ F per km. If it carries an ac of frequency 5 kHz, what should be the value of an inductor required to be connected in series so that the impedance of the circuit is minimum
The reading of voltmeter in the circuit shown will be
An ac source of angular frequency ω is fed across a resistor r and a capacitor C in series. The current registered is I. If now the frequency of source is changed to ω /3 (but maintaining the same voltage), the current in then circuit is found to be halved. Calculate the ratio of reactance to resistance at the original frequency ω
In the adjoining figure the impedance (in ohm) of the circuit will be
If i = t 2 0 < t < T then r.m.s. value of current is
Is it possible
The figure shows variation of R, X L and X C with frequency f in a series L, C, R circuit. Then for what frequency point, the circuit is inductive
An alternating emf is applied across a parallel combination of a resistance R, capacitance C and an inductance L. If I R , I L , I C are the currents through R, L and C respectively, then the diagram which correctly represents, the phase relationship among I R , I L , I C and source emf E, is given by
The r.m.s. voltage of the wave form shown is
A constant voltage at different frequencies is applied across a capacitance C as shown in the figure. Which of the following graphs Correctly depicts the variation of current with frequency ?
The output current versus time curve of a rectifier is shown in the figure. The average value of output current in this case is
When an ac source of e.m.f. e = E 0 sin ( 100 t ) is connected across a circuit, the phase difference between the e.m.f. e and the current i in the circuit is observed to be π / 4 , as shown in the diagram. If the circuit consists possibly only of RC or LC in series, find the relationship between the two elements
Two sinusoidal voltages of the same frequency are shown in the diagram. What is the frequency, and the phase relationship between the voltages
In pure inductive circuit, the curves between frequency f and reciprocal of inductive reactance 1/X L is
The vector diagram of current and voltage for a circuit is as shown. The components of the circuit will be
The resonance point in X L − f and X C − f curves is
The i – v curve for anti-resonant circuit is
The graphs given below depict the dependence of two reactive impedances X 1 and X 2 on the frequency of the alternating e.m.f. applied individually to them. We can then say that
Which of the following plots may represent the reactance of a series LC combination
A bulb and a capacitor are in series with an ac source. On increasing frequency how will glow of the bulb change
The r.m.s. current in an ac circuit is 2 A. If the wattless current be 3 A , what is the power factor
2 .5 π μF capacitor and 3000-ohm resistance are joined in series to an ac source of 200 volt and 50 sec − 1 frequency. The power factor of the circuit and the power dissipated in it will respectively
The self inductance of a choke coil is 10 mH. When it is connected with a 10V dc source, then the loss of power is 20 watt. When it is connected with 10 volt ac source loss of power is 10 watt. The frequency of ac source will be
A group of electric lamps having a total power rating of 1000 watt is supplied by an ac voltage E = 200 sin ( 310 t + 60 ° ) . Then the r.m.s. value o the circuit current is
Following figure shows an ac generator connected to a “block box” through a pair of terminals. The box contains possible R, L, C or their combination, whose elements and arrangements are not known to us. Measurements outside the box reveals that e = 75 sin (sin ω t) volt, i = 1.5 sin ( ω t + 45 o ) amp then, the wrong statement is
A resistor R, an inductor L and a capacitor C are connected in series to an oscillator of frequency n. if the resonant frequency is n r , then the current lags behind voltage, when
If power factor is 1/2 in a series RL circuit R = 100 Ω . ac mains is used then L is
What will be the self inductance of a coil, to be connected in a series with a resistance of π 3 Ω such that the phase difference between the emf and the current at 50 Hz frequency is 30°
The instantaneous values of current and emf in an ac circuit are I = 1 / 2 sin 314 t amp and E = 2 sin ( 314 t − π / 6 ) V respectively. The phase difference between E and I will be
What is the r.m.s. value of an alternating current which when passed through a resistor produces heat which is thrice of that produced by a direct current of 2 amperes in the same resistor
A LC circuit is in the state of resonance. If C = 0 .1 μF and L = 0 .25 henry. Neglecting ohmic resistance of circuit, what is the frequency of oscillations?
An oscillator circuit consists of an inductance of 0.5mH and a capacitor of 20 μ F . The resonant frequency of the circuit is nearly
Which of the following does not depend upon the magnetic effect of some sort
Dynamo is a device for converting
What is increased in step-down transformer
In transformer, core is made of soft iron to reduce
The ratio of secondary to the primary turns in a transformer is 3 : 2. If the power output be P, then the input power neglecting all loses must be equal to
A step-down transformer is connected to 2400 volts line and 80 amperes of current is found to flow in output load. The ratio of the turns in primary and secondary coil is 20 : 1. If transformer efficiency is 100%, then the current flowing in primary coil will be
The primary winding of a transformer has 100 turns and its secondary winding has 200 turns. The primary is connected to an ac supply of 120 V and the current flowing in it is 10 A. The voltage and the current in the secondary are
A loss free transformer has 500 turns on its primary winding and 2500 in secondary. The meters of the secondary indicate 200 volts at 8 amperes under these conditions. The voltage and current in the primary is
An ideal transformer has 100 turns in the primary and 250 turns in the secondary. The peak value of the ac is 28 V. The r.m.s. secondary voltage is nearest to
In a step-up transformer, the turn ratio is 1 : 2. A Leclanche cell (e.m.f. 1.5V) is connected across the primary. The voltage developed in the secondary would be
The efficiency of transformer is very high because
A transformer connected to 220 volt line shows an output of 2 A at 11000 volt. The efficiency is 100%. The current drawn from the line is
A transformer is used to
A step up transformer connected to a 220 V AC line is to supply 22 kV for a neon sign in secondary circuit. In primary circuit a fuse wire is connected which is to blow when the current in the secondary circuit exceeds 10 mA. The turn ratio of the transformer is
The number of turns in the primary coil of a transformer is 200 and the number of turns in the secondary coil is 10. If 240 volt AC is applied to the primary, the output from the secondary will be
The primary winding of transformer has 500 turns whereas its secondary has 5000 turns. The primary is connected to an ac supply of 20 V, 50 Hz. The secondary will have an output of
In a transformer, the number of turns in primary coil and secondary coil are 5 and 4 respectively. If 240 V is applied on the primary coil, then the ratio of current in primary and secondary coil is
A step-down transformer is connected to main supply 200V to operate a 6V, 30W bulb. The current in primary is
Voltage in the secondary coil of a transformer does not depend upon.
The ratio of secondary to primary turns is 9 : 4 If power input is P, what will be the ratio of power output (neglect all losses) to power input
In a step-up transformer the turn ratio is 1:10. A resistance of 200 ohm connected across the secondary is drawing a current of 0.5 A. What is the primary voltage and current
An ideal transformer has 500 and 5000 turn in primary and secondary windings respectively. If the primary voltage is connected to a 6V battery then the secondary voltage is
In a step-up transformer the voltage in the primary is 220 V and the current is 5A. The secondary voltage is found to be 22000V. The current in the secondary (neglect losses) is
In a primary coil 5A current is flowing on 220 volts. In the secondary coil 2200V voltage produces. Then ratio of number of turns in secondary coil and primary coil will be
In a transformer, the number of turns in primary and secondary are 500 and 2000 respectively. If current in primary is 48 A, the current in the secondary is
The induction coil works on the principle of
A transformer has turn ratio 100/1. If secondary coil has 4 amp current then current in primary coil is
The number of turns in primary and secondary coils of a transformer are 100 and 20 respectively. If an alternating potential of 200 volt is applied to the primary, the induced potential in secondary will be
Quantity that remains unchanged in a transformer is
