Alternating current practice · Mixed difficulty

The $Q$-factor of a series L-C-R resonant circuit depends on

A resistance of 20 ohms is connected to a source of an alternating potential $V = 220\sin \left[ {100\,\pi \,t} \right]$. The time taken by the current to change from its peak value to r.m.s. value is [in sec]

An AC supply gives 30 V r.m.s which passes through a $10\,\,\Omega$ resistance. The power dissipated in it is [wats]

Assertion: Capacitor serves as a block for dc and offers an easy path to ac.

Reason: Capacitive reactance is inversely proportional to frequency.

The armature of a DC motor has a resistance of 20 Ω. It draws a current of 1.5 A when run by 220 V DC. The value of peak emf induced in it will be

A transmitter transmits at a wavelength of $300 \mathrm{~m}$. A condenser of capacitance $2.4 \mu \mathrm{F}$ is being used. The value of the inductance for the resonant circuit is approximately

A coil of resistance $40 \, \Omega$ is connected across a $4.0 \mathrm{~V}$ battery. $0 . 10 \mathrm{~s}$ after the battery is connected, the current in the coil is $63 \mathrm{~mA}$. Find the inductance of the coil.

Assertion: Average value of ac over a complete cycle is always zero.

Reason: Average value of ac is always defined over half cycle.

Statement (A): The inductive reacance limits the current in a purely inductive ciruit in the same way as the resistance circuit.

Statement (B): The inductive reatance is directly proportional to the inductance and to the frequency of the varying current.

A circuit consists of an inductance of 0.5 mH and a capacitor of 20μF. The frequency of the L – C oscillations is approximately

The ratio of secondary to primary turns is $\mathrm{9 : 4}$. If power input is $P$, what will be the ratio of power output (neglect all losses) to power input

An inductance $L$ and a resistance $R$ are first connected to a battery. After some time the battery is disconnected but $L$ and $R$ remain connected in a closed circuit. Then the current reduces to $\mathrm{37}\,\,\mathrm{\% }$ of its initial value in

Large transformers, when used for some time, become hotand are cooled by circulating oil. The heating of transformer is due to

For a series L-C-R circuit at resonance, the statement which is not true is

The resistance of a coil for DC is in ohms. In AC, the
resistance:

In a pure inductive circuit the induced emf

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

In an ac circuit, the potential differences across an inductance and resistance joined in series are, respectively, $16 \mathrm{~V}$ and $20 \mathrm{~V}$. The total potential difference across the circuit is

A condenser of capacity $20 \mu \mathrm{F}$ is first charged and then discharged through a $10 \mathrm{~mH}$ inductance. Neglecting the resistance of the coil, the frequency of the resulting vibrations will be

Statement-A : A hot wire ammeter reads the RMS value of current.

Statement-B : A hot wire ammeter can read AC but cannot read DC.

The correct statement(s) is/are

The peak value of an alternating voltage applied to a $50 ~\Omega$ resistance is $10 \mathrm{~V}$. Find the rms current. If the voltage frequency is $100 \mathrm{~Hz}$, write the equation for the instantaneous current.

A coil has an inductance of $0.7 \mathrm{~H}$ and is joined in series with a resistance of $220 ~\Omega$. Find the wattless component of the current in the circuit, when an alternating emf of $220 \mathrm{~V}$ at a frequency of $50 \mathrm{~Hz}$ is supplied to it.

Given below are two statements:
Statement-I: The reactance of an ac circuit is zero. It is possible that the circuit contains a capacitor and an inductor.
Statement-II: In ac circuit, the average power delivered by the source never becomes zero.
In the light of the above statements, choose the correct answer from the options given below.

The frequency for which a $5\;\mu F$ capacitor has a reactance of $\frac{1}{{1000}}\,\,\,\mathrm{ohm}$ is given by

For an LCR series circuit with an A.C. source of angular frequency $\omega$

If the capacity of a condenser is 1 F, then its resistance in a DC circuit will be

A cell of 6 volt is connected across an inductor of 4 mH in series with a $2\,\,\,\Omega$ resistor. What is the rate of growth of current immediately after the cell is switched on $\left[ {A{S^{ - 1}}} \right]$

Hot wire ammeters can be used for measuring:

The peak value of A.C. is $4 \sqrt{2} A$. It's apparent value will be

Statement (A): The power consumed in an electric circuit is never negative
Statement (B): The average power consumed in an electric circuit is ${P}=\frac{{V}^2}{{R}}={I}^2{R}$