Alternating Current — practice questions
136 curated practice questions from Alternating Current (Physics Class 12, CBSE) — 110 easy, 3 hard, 23 medium. Every question includes the final answer free; step-by-step worked solutions with a free account.
- When a voltage measuring device is connected to ac mains, the meter shows the steady input voltage of 220 V. This means
- A 44 mH inductor is connected to 220 V, 50 Hz ac supply. The rms value of the current in the circuit is
- A sinusoidal voltage of peak value 293 V and frequency 50 Hz is applied to a series LCR circuit in which R = 6 Ω, L =…
- The resonant frequency of a series LCR circuit with L = 2.0 H, C = 32 μF and R = 10 Ω is
- Electrical energy is transmitted over large distances at high alternating voltage. Which of the following statements is…
- A charged 30 μF capacitor is connected to a 27 mH inductor. The angular frequency of free oscillations of the circuit is
- An alternating current generator has an internal resistance R g and an internal reactance X g . It is used to supply…
- Assertion(A): In an ideal step-down transformer, the electrical energy is not lost. Reason (R): In a step-down…
- An ammeter connected in series in an ac circuit reads 10 A. The maximum value of current at any instant in the circuit…
- An inductor of 30 mH is connected to a 220 V, 100 Hz ac source. The inductive reactance is
- The primary and secondary coils of a transformer have 500 turns and 5000 turns respectively. The primary coil is…
- Figure shows a series LCR circuit connected to a variable frequency 230 V source. The source frequency which drives the…
- Which of the following combinations should be selected for better tuning of an LCR circuit used for communication?
- An LCR series circuit is under resonance. If I m is current amplitude, V m is voltage amplitude, R is the resistance, Z…
- A transformer is used to light 140 W, 24 V lamp from a 240 V ac mains. If the main current is 0.7 A, the efficiency of…
- The voltage over a cycle varies as The average value of the voltage for one cycle is
- Quality factor and power factor both have the dimensions of
- A 60 W load is connected to the secondary of an ideal transformer whose primary draws line voltage. If a current of…
- Which of the following graphs represents the correct variation of capacitive reactance X C with frequency υ ?
- In a series LCR circuit the voltage across the resistance, capacitance and inductance is 10 V each. If the capacitance…
- An ac source is of 200 2 V, 50 Hz. The value of voltage after s from the start is
- Power dissipated in an LCR series circuit connected to an ac source of emf ε is
- A planar loop is rotated in a magnetic field about an axis perpendicular to the field. The polarity of induced emf…
- An iron cored coil is connected in series with an electric bulb with an AC source as shown in figure. When iron piece…
- A coil of an ac generator, having 100 turns and area 0.1 m ^ 2 each, rotates at half a rotation per second in a…
- A capacitor of capacitance C has reactance X in an ac circuit. If the capacitance and the frequency of the applied…
- An LC circuit contains a 40 mH inductor and a 25 m F capacitor. The resistance of the circuit is negligible. The time…
- An ac source of voltage V = V m sin w t is connected across the resistance R as shown in figure. The phase relation…
- The ratio of the number of turns of the primary to the secondary coils in an ideal transformer is 20: 1 . If 240 V ac…
- The core of a transformer is laminated to reduce the effect of
- A fully charged capacitor C with initial charge Q 0 is connected to a coil of self inductance L at t = 0. The time at…
- An inductor of reactance 1 Ω and a resistor of 2 Ω are connected in series to the terminals of a 6 V (rms) ac source…
- The Q factor of a series LCR circuit with L = 2 H, C = 32 μF and R = 10 Ω is
- In a series LCR circuit, the phase difference between the voltage and the current is 45°. Then the power factor will be
- A small signal voltage V(t) = V 0 sin t is applied across an ideal capacitor C.
- The power factor of the circuit as shown in figure is
- When an ac voltage of 220 V is applied to the capacitor C , then
- An alternating current is given by I = I _ 0 (100 ) t . The least time the current takes to decrease from its maximum…
- Assertion (A): If the frequency of the applied AC is doubled, then the power factor of a series R-L circuit decreases…
- A resistor and an ideal inductor are connected in series to a 100 2 ~V , 50 Hz ac source. When a voltmeter is connected…
- In a circuit, L, C and R are connected in series with an alternating voltage source of frequency υ. The current leads…
- If a capacitor of 8 μF is connected to a 220 V, 100 Hz ac source and the current passing through it is 65 mA, then the…
- A 60 μF capacitor is connected to a 110 V (rms), 60 Hz ac supply. The rms value of current in the circuit is
- An inductor 200 mH, capacitor 500 F and resistor 10 are connected in series with a 100 V variable frequency ac source…
- A 30 µF capacitor is connected to a 150 V, 60 Hz ac supply. The rms value of current in the circuit is
- An electrical device draws 2 kW power from ac mains voltage 223 V(rms). The current differs lags in phase by = ^ -1 (…
- An ac source V =282 (100 t ) volt is connected across a 1 ~F capacitor. The rms value of current in the circuit will be…
- A small town with a demand of 800 kW of electric power at 220 V is situated 15 km away from an electric plant…
- The alternating current I in an inductor is observed to vary with time t as shown in the graph for a cycle. Which one…
- The relation between an AC voltage source and time in SI units is V = 120 (100 t) (100 t) V. The value of peak voltage…
- A voltage u= u_ 0 t applied to a circuit drives a current i = i _ 0 ( t + ) in the circuit. The average power consumed…
- A circuit is made up of a resistance 1 Ω and inductance 0.01 H. An alternating voltage of 200 V at 50 Hz is connected…
- When an ac source of voltage V = V 0 sin100 t is connected across a circuit, the phase difference between the voltage V…
- In a uniform magnetic field B a wire in the form of a semicircle of radius r rotates about the diameter of the circle…
- In an ideal inductor, L = 4H and = 100 rad/s. The power developed is:
- In an alternating current circuit consisting of elements in series, the current increases on increasing the frequency…
- A power transmission line feeds input power at 2400 V to a step down transformer with its primary windings having 4000…
- A capacitor of capacity C has reactance X. If capacitance and frequency are doubled, the reactance would be:
- In which of the following circuits the maximum power dissipation is observed?
- The rms value of current in an ac circuit is 25 A, then peak current is
- In the series LCR circuit shown, the impedance is
- Alternating voltage ( V ) is represented by the equation
- At resonant frequency the current amplitude in series LCR circuit is
- In a series LCR circuit the voltage across an inductor, capacitor and resistor are 20 V, 20 V and 40 V respectively…
- In the question number 26, the net power consumed over a full cycle is
- An LC circuit contains a 20 mH inductor and a 25 m F capacitor with an initial charge of 5 mC. The total energy stored…
- When an alternating voltage E = E 0 sin t is applied to a circuit, a current I = I 0 sin ( t+ 2 ) flows through it. The…
- In a series LCR circuit having L = 30 mH, R = 8 Ω and the resonant frequency is 50 Hz. The quality factor of the…
- A transformer has 100 turns in the primary coil and carries 8 A current. If input power is 1 kW, the number of turns in…
- If V = 100sin(100 t ) V and I = 100sin (100 t+ 3 ) mA are the instantaneous values of voltage and current, then the rms…
- An alternating voltage (in volts) given by V=200 2 (100 t) is connected to 1 μF capacitor through an ideal ac ammeter…
- A series resonant LCR circuit has a quality factor ( Q -factor) 0.4. If R = 2 k , C = 0.1 F , then the value of…
- When the plane of the armature of an a.c. generator is parallel to the field, in which it is rotating
- In the question number 20, the phase difference between the voltage across the source and current is
- Which of the following quantity/quantities remains same in primary and secondary coils of an ideal transformer?…
- Which of the following assumptions has been used to obtain the relation v_ s v_ p = N_ s N_ p for a transformer?
- In an ac circuit, V and I are given by V = 150sin(150 t ) volt and I = 150sin ampere. The power dissipated in the…
- An ideal inductor is connected across an AC source of voltage. The current in the circuit
- The number of turns between different pairs of output terminals are shown for a step-up transformer. Input voltage of…
- A pure resistive circuit element X when connected to an ac supply of peak voltage 200 V gives a peak current of 5 A…
- When a wire loop is rotated in a magnetic field, the direction of induced emf changes in every
- The line that draws power supply to your house from street has
- Figure shows the variation of inductive reactance X _ L of two ideal inductors of inductance L_ 1 and L_ 2 , with…
- Transmission lines transmit a voltage of V volt to our houses from power stations, then the power P supplied by them is…
- 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…
- In a transformer the transformation ratio is 0.3. If 220 V ac is fed to the primary, then the voltage across the…
- A 100 resistance and a capacitor of 100 reactance are connected in series across a 220 V source. When the capacitor is…
- In a step up transformer the turn ratio is 1 : 2. A Leclanche cell (emf = 1.5 V) is connected across the primary. The…
- The loss of energy in the form of heat in the iron core of a transformer is
- The voltage across a pure inductor is represented in the figure. Which one of the following curves in the figure will…
- A 100 μF capacitor in series with a 40 Ω resistor is connected to a 100 V, 60 Hz supply. The maximum current in the…
- Assertion (A): A step-up transformer cannot be used as a step-down transformer. Reason (R): A transformer works only in…
- In a series LCR circuit, the plot of I m vs w is shown in the figure. The bandwidth of this plot will be
- The rms value of potential difference V shown in the figure is
- A choke is preferred to resistance for limiting current in ac circuit because
- To reduce the resonant frequency in a series LCR circuit with a generator:
- In a circuit, the current lags behind the voltage by a phase difference of /2 . The circuit contains which of the…
- In the question number 47, the net power absorbed by the circuit in one complete cycle is
- A series LCR circuit with R = 22 Ω, L = 1.5 H and C = 40 μF is connected to a variable frequency 220 V ac supply. When…
- For an LCR circuit, the power transferred from the driving source to the driven oscillator is P = I^2 Z . Then
- A boy peddles a stationary bicycle the pedals of the bicycle are attached to a 200 turn coil of area 0.10 m 2 . The…
- Which of the following graphs represents the correct variation of inductive reactance X L with frequency υ?
- The alternating current I in an inductor is observed to vary with time t as shown in the graph for a cycle. Which one…
- An alternating supply of 220 V is applied across a circuit with resistance 22 Ω and impedance 44 Ω. The power…
- The average value of voltage of 220 V ac mains during its positive half cycle will be:
- A voltage of peak value 283 V and varying frequency is applied to series LCR combination in which R = 3Ω, L = 25 mH and…
- A bulb is rated (100 ~W , 110 ~V ) . It is operated by current of 1.0 A supplied by a step down transformer. If the…
- A circular coil of radius 6 cm and 20 turns rotates about its vertical diameter with an angular speed of 40 rad s –1 in…
- In series LCR circuit, the phase angle between supply voltage and current is
- In the question number 4, the peak voltage of the source is
- In the question number 31, the number of turns in the secondary is
- A transformer is connected to a 200 V ac source. The transformer supplies 3000 V to a device. If the number of turns in…
- A resistor of 500 Ω and an inductance of 0.5 H are in series with an ac source which is given by V = sin(1000 t ). The…
- An ac voltage is applied across an ideal inductor. The current in it
- A 100 resistor is connected to a 220 V, 50 Hz ac supply. The rms value of current in the circuit is
- An LCR series ac circuit is at resonance with 10 V each across L, C and R . If the resistance is halved, the respective…
- 200 V ac source is fed to series LCR circuit having X L = 50 Ω, X C = 50 Ω and R = 25 Ω. Potential drop across the…
- The r.m.s. value of a current given by i = ( i _ 1 t + i _ 2 t ) is -
- A 220 V ac supply is connected between points A and B as shown in figure. What will be the potential difference V…
- The figure shows variation of current (I) with time (t) in four devices P, Q, R and S. The device in which an…
- The current drawn by the primary of a transformer, which steps down 200 V to 20 V to operate a device of resistance 20…
- A 5 μF capacitor is connected to a 200 V, 100 Hz ac source. The capacitive reactance is
- The peak voltage of an ac supply is 440 V, then its rms voltage is
- A step down transformer converts transmission line voltage from 11000 V to 220 V. The primary of the transformer has…
- A series LCR circuit has R = 5 W , L = 40 mH and C = 1 m F, the bandwidth of the circuit is
- A coil of 0.01 H inductance and 1 Ω resistance is connected to 200 V, 50 Hz ac supply. The time lag between maximum…
- As the frequency of an ac circuit increases, the current first increases and then decreases. What combination of…
- At resonance frequency the impedance in series LCR circuit is
- In the question number 69, the time lag between the current maximum and the voltage maximum is
- An ideal inductor is in turn put across 220 V, 50 Hz and 220 V, 100 Hz supplies. The current flowing through it in the…
- In an electrical circuit, R , L , C and ac voltage source are all connected in series. When L is removed from the…
- If a variable frequency ac source is connected to a capacitor then with decrease in frequency the displacement current…
- A 0.2 kΩ resistor and 15 μF capacitor are connected in series to a 220 V, 50 Hz ac source. The impedance of the circuit…
- The output of a step-down transformer is measured to be 24 V when connected to a 12 watt light bulb. The value of the…
- In a pure capacitive circuit if the frequency of ac source is doubled, then its capacitive reactance will be
- The phase relationship between current and voltage in a pure resistive circuit is best represented by