Alternating Current

A 750 Hz, 20 V (rms) source is connected to a
resistance of 100 \(\Omega\), an inductance of 0.1803 H
and a capacitance of 10 \(\mu\)F all in series. The
time in which the resistance (heat capacity
2 J/oC) will get heated by 10oC. (assume...

An inductance coil has a reactance of 100 \(\Omega\).
When an AC signal of frequency 1000 Hz is
applied to the coil, the applied voltage leads
the current by 45o. The self-inductance of the
coil is

A power transmission line feeds input power at 2300 V to a srep down transformer with its primary windings having 4000 turns. The output power is delivered at 230 V by the transformer. If the current in the primary of the transformer is 5A ...

A series AC circuit containing an inductor (20 mH), a capacitor (120 \(\mu\)F) and a resistor (60 \(\Omega\)) is driven by an AC source of 24V/50 Hz. The energy dissipated in the circuit in 60 s is :

An alternating voltage v(t) = 220 sin 100 \(\pi\)t volt
is applied to a purely resistance load of 50\(\Omega\) .
The time taken for the current to rise from half
of the peak value to the peak value is :

A circuit connected to an ac source of emf
e = e0sin(100t) with t in seconds, gives a phase
difference of \(\pi\)/4 between the emf e and
current i. Which of the following circuits will
exhibit this ?

In the figure shown, a circuit contains two identical resistors with resistance R = 5\(\Omega\) and an inductance with L = 2mH. An ideal battery of 15 V is connected in the circuit. What will be the current through the battery long after t...

In the above circuit, C = \({{\sqrt 3 } \over 2}\)\(\mu\)F, R2 = 20 \(\Omega\), L = \({{\sqrt 3 } \over {10}}\) H and R1 = 10 \(\Omega\). Current in L-R1 path is I1 and in C-R2 path it is I2 . The voltage of A.C. source is given by, V = ...

Consider the LR circuit shown in the figure. If the switch S is closed at t = 0 then the amount of charge that
passes through the battery between t = 0 and t = \({L \over R}\)
is :

In the circuit shown,

the switch S1 is closed at time t = 0 and the switch S2 is kept open. At some later time(t0), the switch S1 is opened and S2 is closed. The behavior of the current I as a function of time 't' is given by :

A transformer consisting of 300 turns in the
primary and 150 turns in the secondary gives
output power of 2.2 kW. If the current in the
secondary coil is 10A, then the input voltage
and current in the primary coil are :

A coil of self inductance 10 mH and resistance 0.1 \(\Omega\) is connected through a switch to a battery of internal
resistance 0.9 \(\Omega\). After the switch is closed, the time taken for the current to attain 80% of the saturation
val...

A power transmission line feeds input power at 2300 V to a step down transformer with its primary windings having 4000 turns, giving the output power at 230 V. If the current in the primary of the transformer is 5 A, and its efficiency i...

An ideal capacitor of capacitance \(0.2\,\mu F\) is charged to a potential difference of \(10\) \(V.\) The charging battery is then disconnected. The capacitor is then connected to an ideal inductor of self inductance \(0.5\) \(mH.\) The cu...

In an a.c. circuit, the instantaneous e.m.f. and current are given by
e = 100 sin 30 t
i = 20 sin \(\left( {30t - {\pi \over 4}} \right)\)
In one cycle of a.c., the average power consumed by the circuit and the wattless current are, respe...

For an RLC circuit driven with voltage of amplitude vm and frequency \({\omega _0}\) = \({1 \over {\sqrt {LC} }}\) the current exhibits resonance. The quality factor, Q is given by :

A sinusoidal voltage of peak value 283 V and angular frequency 320/s is applied to a series LCR circuit. Given that R=5 \(\Omega\), L=25 mH and C=1000 \(\mu\)F. The total impedance, and phase difference between the voltage across the sour...

A series LR circuit is connected to a voltage source with
V(t) = V0 sin\(\Omega\)t. After very large time, current I(t) behaves as
(t0 >> \({L \over R}\)) :

An arc lamp requires a direct current of
10 A at 80 V to function. If it is connected
to a 220 V (rms), 50 Hz AC supply, the
series inductor needed for it to work is
close to :

An inductor \((L=0.03\) \(H)\) and a resistor \(\left( {R = 0.15\,k\Omega } \right)\) are connected in series to a battery of \(15V\) \(EMF\) in a circuit shown below. The key \({K_1}\) has been kept closed for a long time. Then at \(t=0\),...

An \(LCR\) circuit is equivalent to a damped pendulum. In an \(LCR\) circuit the capacitor is charged to \({Q_0}\) and then connected to the \(L\) and \(R\) as shown below :

If a student plots graphs of the square of maximum charge $$\lef...

In the circuit shown here, the point \('C'\) is kept connected to point \('A'\) till the current flowing through the circuit becomes constant. Afterward, suddenly, point \('C'\) is disconnected from point \('A'\) and connected to point $$'...

In an \(LCR\) circuit as shown below both switches are open initially. Now switch \({S_1}\) is closed, \({S_2}\) kept open. (\(q\) is charge on the capacitor and \(\tau\) \(=RC\) is Capacitance time constant). Which of the following statem...

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 which the energy is stored equally between the electric and the magnetic fields is :

A resistor \('R'\) and \(2\mu F\) capacitor in series is connected through a switch to \(200\) \(V\) direct supply. Across the capacitor is a neon bulb that lights up at \(120\) \(V.\) Calculate the value of \(R\) to make the bulb light up ...

In a series \(LCR\) circuit \(R = 200\Omega\) and the voltage and the frequency of the main supply is \(220V\) and \(50\) \(Hz\) respectively. On taking out the capacitance from the circuit the current lags behind the voltage by $${30^ \ci...

In the circuit shown below, the key \(K\) is closed at \(t=0.\) The current through the battery is

An inductor of inductance \(L=400\) \(mH\) and resistors of resistance \({R_1} = 2\Omega\) and \({R_2} = 2\Omega\) are connected to a battery of \(emf\) \(12\) \(V\) as shown in the figure. The internal resistance of the battery is neglig...

In an \(a.c.\) circuit the voltage applied is \(E = {E_0}\,\sin \,\omega t.\) The resulting current in the circuit is \(I = {I_0}\sin \left( {\omega t - {\pi \over 2}} \right).\) The power consumption in the circuit is given by

In an \(AC\) generator, a coil with \(N\) turns, all of the same area \(A\) and total resistance \(R,\) rotates with frequency \(\omega\) in a magnetic field \(B.\) The maximum value of \(emf\) generated in the coil is

In a series resonant \(LCR\) circuit, the voltage across \(R\) is \(100\) volts and \(R = 1\,k\Omega\) with \(C = 2\mu F.\) The resonant frequency \(\omega\) is \(200\) \(rad/s\). At resonance the voltage across \(L\) is

The phase difference between the alternating current and \(emf\) is \({\pi \over 2}.\) Which of the following cannot be the constituent of the circuit?

A circuit has a resistance of \(12\) \(ohm\) and an impedance of \(15\) \(ohm\). The power factor of the circuit will be

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

Alternating current can not be measured by \(D.C.\) ammeter because

In an \(LCR\) series \(a.c.\) circuit, the voltage across each of the components, \(L,C\) and \(R\) is \(50V\). The voltage across the \(L.C\) combination will be :

In a \(LCR\) circuit capacitance is changed from \(C\) to \(2\) \(C\). For the resonant frequency to remain unchaged, the inductance should be changed from \(L\) to

In an oscillating \(LC\) circuit the maximum charge on the capacitor is \(Q\). The charge on the capacitor when the energy is stored equally between the electric and magnetic field is

The core of any transformer is laminated so as to

The power factor of \(AC\) circuit having resistance \((R)\) and inductance \((L)\) connected in series and an angular velocity \(\omega\) is

In a transformer, number of turns in the primary coil are \(140\) and that in the secondary coil are \(280.\) If current in primary coil is \(4A,\) then that in the secondary coil is