Alternating Current

An alternating e.m.f. is \(\mathrm{e}=\mathrm{e}_0 \sin \omega \mathrm{t}\). In what time the e.m.f. will have half its maximum value, if '\(\mathrm{e}\)' starts from zero? (\(\mathrm{T}=\) time period, \(\sin 30^{\circ}=0.5\))

In series LCR circuit, at resonance the peak value of current will be [\(\mathrm{E_0}\) is peak emf, R is resistance, \(\omega \mathrm{L}\) is inductive reactance and \(\omega \mathrm{C}\) is capacitive]

A rejector circuit is the resonant circuit in which

For series LCR circuit, which one of the following is a CORRECT statement?

If we increase the frequency of an a.c. supply, then inductive reactance

In an LCR series a.c. circuit, the voltage across each of the components L, C and R is 60 V. The voltage across the LC combination is

A circuit containing resistance R\(_1\), inductance L\(_1\) and capacitance C\(_1\) connected in series resonates at the same frequency 'f\(_0\)' as another circuit containing R\(_2\), L\(_2\) and C\(_2\) in series. If two circuits are conn...

A series L-C-R circuit containing a resistance of \(120 ~\Omega\) has angular frequency \(4 \times 10^5 \mathrm{~rad} \mathrm{~s}^{-1}\). At resonance the voltage across resistance and inductor are \(60 \mathrm{~V}\) and \(40 \mathrm{~V}\) ...

The frequency of the output signal of an LC oscillator circuit is '\(\mathrm{F}\)' Hz with a capacitance of 0.1 \(\mu \mathrm{F}\). If the value of the capacitor is increased to \(0.2~ \mu \mathrm{F}\), then the frequency of the output sign...

In an a.c. circuit, a resistance R = 40 \(\Omega\) and an inductance 'L' are connected in series. If the phase angle between voltage and current is 45\(^\circ\), then the value of the inductive reactance is (tan 45\(^\circ\) = 1)

An a.c. source of angular frequency '\(\omega\)' 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 \(\frac{\omega}{3}\) (but maintaining the same vo...

For the circuit shown below, instantaneous current through inductor '\(\mathrm{L}\)' and capacitor '\(\mathrm{C}\)' is respectively.

A parallel plate capacitor having plates of radius 6 cm has capacitance 100 pF. It is connected to 230 V a.c. supply with angular frequency 300 rad/s. The r.m.s. value of current is

A step down transformer is used to reduce the main supply from '\(V_1\)' volt to '\(V_2\)' volt. The primary coil draws a current '\(\mathrm{I}_1\)' \(\mathrm{A}\) and the secondary coil draws '\(\mathrm{I}_2\)' A. $$(\mathrm{I}_1<\mathrm{I...

A step down transformer has turns ratio \(20: 1\). If \(8 \mathrm{~V}\) is applied across \(0.4 \mathrm{~ohm}\) secondary then the primary current will be

A capacitor of capacity '\(C\)' is charged to a potential '\(V\)'. It is connected in parallel to an inductor of inductance '\(\mathrm{L}\)'. The maximum current that will flow in the circuit is

A series combination of resistor 'R' and capacitor 'C' is connected to an a.c. source of angular frequency '\(\omega\)'. Keeping the voltage same, if the frequency is changed to \(\frac{\omega}{3}\) the current becomes half of the original ...

An alternating voltge is represented by \(\mathrm{V}=80 \sin (100 \pi \mathrm{t}) \cos (100 \pi \mathrm{t})\) volt. The peak voltage is

In the graphical representation of e.m.f. '\(\mathrm{e}\)' and current '\(\mathrm{i}\)' versus '\(\omega \mathrm{t}\)' for an a.c. circuit, both emf and current reach zero, minimum and maximum value at the same time. The circuit element con...

In a step up transformer, which one of the following statements is correct?

The instantaneous value of an alternating current is given by \(\mathrm{i}=50 \sin (100 \pi \mathrm{t})\). It will achieve a value of \(25 \mathrm{~A}\) after a time interval of \(\left(\sin 30^{\circ}=0.5\right)\)

Three pure inductors each of inductance 6H are connected as shown in the figure. Their equivalent inductance between the points 'P' and 'Q' is

The inductive reactance of a coil is R\(\Omega\). If the inductance of a coil is doubled and frequency of a.c. supply is also doubled then the new inductive reactance will be

In LCR series resonant circuit, at resonance, voltage across 'L' and 'C' will cancel each other because they are

An inductor coil takes current 8A when connected to an 100 V and 50 Hz a.c. source. A pure resistor under the same condition takes current of 10A. If inductor coil and resistor are connected in series to an 100V and 40 Hz a.c. supply, then ...

An inductor coil wound uniformly has self inductance
'L' and resistance 'R'. The coil is broken into two identical parts. The two parts are then connected in parallel across a battery of 'E' volt of negligible internal resistance. The cur...

When a d.c. voltage of \(200 \mathrm{~V}\) is applied to a coil of self-inductance \(\left(\frac{2 \sqrt{3}}{\pi}\right) \mathrm{H}\), a current of \(1 \mathrm{~A}\) flows through it. But by replacing d.c. source with a.c. source of $$200 \...

A series LCR circuit with resistance (R) \(500 ~\mathrm{ohm}\) is connected to an a.c. source of \(250 \mathrm{~V}\). When only the capacitance is removed, the current lags behind the voltage by \(60^{\circ}\). When only the inductance is r...

In an ideal step down transformer, out of the following quantities, which quantity increases in the secondary coil?

An inductive coil has a resistance of \(100 ~\Omega\). When an a.c. signal of frequency \(1000 \mathrm{~Hz}\) is applied to the coil the voltage leads the current by \(45^{\circ}\). The inductance of the coil is $$\left(\tan 45^{\circ}=1\ri...

An AC circuit contains resistance of $12 \Omega$ and inductive reactance $5 \Omega$. The phase angle between current and potential difference will be

An alternating emf of \(0.2 \mathrm{~V}\) is applied across an L-C-R series circuit having \(R=4 \Omega, C=80 \mu \mathrm{F}\) and \(L=200 \mathrm{~mH}\). At resonance the voltage drop across the inductor is

A step-up transformer has 300 turns of primary winding and 450 turns of secondary winding. A primary is connected to 150 V and the current flowing through it is 9A. The current and voltage in the secondary are

A coil has inductance 2 H . The ratio of its reactance, when it is connected first to an $A C$ source and then to DC source, is

A 220 V input is supplied to a transformer. The output circuit draws a current of 2.0 A at 440 V . If the ratio of output to input power is 0.8 , then the current drawn by primary winding is

In a series $L C R$ circuit $R=300 \Omega, L=0.9 \mathrm{H}$, $C=2 \mu \mathrm{~F}, \omega=1000 \mathrm{rad} / \mathrm{s}$. The impedance of the circuit is

An alternating voltage is given by $E=100 \sin \left(\omega+\frac{\pi}{6}\right) \mathrm{V}$. The voltage will be maximum for the first time when is [ $T=$ periodic time)