Alternating current practice · Medium

Can we use $15 \mathrm{~Hz}$ ac for lighting purposes?

An alternating voltage is represented as $E=20 \sin 300 t$. The average value of voltage over one cycle will be

In the non-resonant circuit, what will be the nature of the circuit for frequencies higher than the resonant frequency

A 10 ohm resistance, 5 mH coil and 10 μF 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

A coil of resistance $R$ and inductance $L$ is connected across an $a.c.$ power supply of $r.m.s.$ voltage ${V}$. The power dissipated in the coil is

An LCR series circuit is compared with a damped oscillator of mass ' ${m}$ ' with force constant ${K}$ and damping coefficient ' ${b}$ '. The correct matching of quantities in damped oscillator analogous with those in LCR circuit is

In a series $L - C - R$ resonance circuit, if we change the resistance only, from a lower to higher value,

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

In a series $L C R$ circuit, at resonance, the bandwidth frequency can be represented as

In a step-up transformer the turn’s ratio is 10. If the frequency of the current in the primary coil is 50Hz then the frequency of the current in the secondary coil will be……… Hz

In $R-L$ series $D C$ circuit $E=20 \mathrm{~V}, L=5 \mathrm{mH}$ and $R=1 \Omega$. If battery is connected at $t=0$ sec. then find time when $\mathbf{I}$ is $12.6 \mathrm{~A}$.

For a series L – C – R circuit, the phase difference between current and voltage at the condition of resonance will be

In an LCR circuit capacitance is changed from $C$ to $2 C$. For the resonant frequency to remain unchanged, the inductance should be changed from $L$ to

A resistance $R$, an inductance $L=0.01 {H}$ and a capacitance $C$ are connected in series. When a voltage $V=400 \cos \left(300 t-10^{\circ}\right) {V}$ is applied to the series combination, the current flowing is $10 \sqrt{2} \cos \left(3000 t-55^{\circ}\right)$ A. Find the capacitance of capacitor in microfarads.

When $100 \mathrm{~V} \mathrm{DC}$ is applied across a solenoid, a current of $1 \mathrm{~A}$ flows in it. When $100 \mathrm{V} \mathrm{~AC}$ is applied across the same coil, the current drops to $0.5 \mathrm{~A}$. If the frequency of the $\mathrm{AC}$ source is $50 \mathrm{~Hz}$, the impedance and inductance of the inductor for the given $\mathrm{AC}$ circuit are

An R-L-C series circuit with $100\,\Omega$ resistance is connected to an AC source of $200 {~V}$ and $\omega=300 \,{rad} / {s}$. When only capacitor is removed, the current lags behind voltage by $60^{\circ}$. When only inductor is removed, the current leads voltage by $60^{\circ}$. The power dissipated in the R-L-C circuit is

Statement (A): An ac emf which oscillates symmetrically about zero, the current it sustains also oscillates symmetrically about zero.

Statement (B): In any circuit element, current is always in the phase with voltage.

A resistance of $300\, \Omega$ and an inductance of $\frac{1}{\pi}$ 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

Assertion: If the frequency of alternating current in an ac circuit consisting of an inductance coil is increased then current gets decreased.

Reason: The current is inversely proportional to frequency of alternating current.

What is the self-inductance of a coil which produces 5 V when the current changes from 3 A to 2 A in one millisecond?

Statement (A): The reactance offered by an inductance in A.C. circuit decreases with increase of A.C frequency.

Statement (B): The reactance offered by a capacitor in A.C circuit increases with increase of A.C frequency.

A series LCR circuit is connected to an ac voltage source. When $\mathrm{L}$ is removed from the circuit, the phase difference
between current and voltage is $\frac{\pi }{3}$. If instead $\mathrm{C}$ is removed from the circuit, the phase difference is again $\frac{\pi }{3}$ between
current and voltage. The power factor of the circuit is:

In AC circuit a resistance of R Ω is connected in series with an inductance L. If the phase difference between the current and voltage is 45°, the inductive reactance will be

Statement (A): In high current low voltage windings of a transformer thick wire is used to minimize energy loss due to heat produced.

Statement (B): The core of any transformer is laminated so as to reduce the energy loss due to eddy currents.

Choke coil is used to control

An AC source producing emf

$e=e_0\left[\cos \left(100 \pi \mathrm{s}^{-1}\right) t+\cos \left(500 \pi \mathrm{s}^{-1}\right) t\right]$

is connected in series with a capacitor and resistor. The steady state current in the circuit is found to be

$I=I_1 \cos \left[\left(100 \pi \mathrm{s}^{-1}\right) t+\phi_1\right]+I_2 \cos \left[\left(500 \pi \mathrm{s}^{-1}\right) t+\phi_2\right]$

A $9 / 100 \pi$ inductor and a $12 \Omega$ resistance are connected in series to a $225 \mathrm{~V}, 50 \mathrm{~Hz}$ ac source. Calculate the current in the circuit and the phase angle between the current and the source voltage.

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

Assertion: With increase in frequency of an A.C supply, the impedance of an L-C-R series circuit, decreases at first, becomes minimum and then increases.

Reason: In L-C-R series circuit, impedance (z)
$z=\sqrt{R^2+\left(X_L-X_C\right)^2}$.

In a step-up transformer, the turn ratio is $\mathrm{1 : 2}$. A Leclanche cell (e.m.f. $\mathrm{1}\mathrm{.5}\,\,\mathrm{V}$) is connected across the primary. The voltage developed in the secondary would be