Alternating Current · Physics · COMEDK
MCQ (Single Correct Answer)
When an A.C. source is connected to a inductive circuit,
In the $$\mathrm{A} . \mathrm{C}$$. circuit given below, voltmeters $$\mathrm{V}_1$$ and $$\mathrm{V}_2$$ read $$100 \mathrm{~V}$$ each. Find the reading of the voltmeter $$\mathrm{V}_3$$ and the ammeter $$\mathrm{A}$$.
A transformer has 400 turns in its primary winding and 800 turns in its secondary winding. The primary voltage is $$20 \mathrm{~V}$$ and the load in the secondary is 4 ohm. The current in the primary, assuming it to be an ideal transformer, is
A group of devices having a total power rating of 500 watt is supplied by an $$\mathrm{AC}$$ voltage $$E=200 \sin \left(3.14 t+\frac{\pi}{4}\right)$$. Then the r.m.s. value of the circuit current is
An AC voltage source of variable angular frequency $$\omega$$ and fixed amplitude $$\mathrm{V}_0$$ is connected in series with a capacitance $$\mathrm{C}$$ and an electric bulb of resistance $$\mathrm{R}$$ (inductance zero). When $$\omega$$ is decreased
A transformer which steps down $$330 \mathrm{~V}$$ to $$33 \mathrm{~V}$$ is to operate a device having impedance $$110 \Omega$$. The current drawn by the primary coil of the transformer is :
A coil of inductance $$1 \mathrm{H}$$ and resistance $$100 \Omega$$ is connected to an alternating current source of frequency $$\frac{50}{\pi} \mathrm{~Hz}$$. What will be the phase difference between the current and voltage?
A coil offers a resistance of $$20 \mathrm{~ohm}$$ for a direct current. If we send an alternating current through the same coil, the resistance offered by the coil to the alternating current will be :
The capacitance of a parallel plate capacitor is $$400 \mathrm{~pF}$$. It is connected to an ac source of $$100 \mathrm{~V}$$ having an angular frequency $$100 \mathrm{~rad~s}^{-1}$$. If the rms value of the current is $$4 \mu \mathrm{A}$$, the displacement current is:
The instantaneous values of alternating current and voltages in a circuit given as
$$\begin{aligned} & i=\frac{1}{\sqrt{2}} \sin (100 \pi t) \mathrm{amp} \\ & e=\frac{1}{\sqrt{2}} \sin (100 \pi t+\pi / 3) \text { volt } \end{aligned}$$
The average power (in watts) consumed in the circuit is
In the series L-C-R circuit shown, the impedance is
In the case of an inductor
In an electrical circuit $$R, L, C$$ and $$\mathrm{AC}$$ voltage source are all connected in series. When $$L$$ is removed from the circuit, the phase difference between the voltage and the current in the circuit is $$\pi / 3$$. If instead $$C$$ is removed from the circuit, the phase difference is again $$\pi / 3$$. The power factor of the circuit is
$$220 \mathrm{~V}$$ ac is more dangerous than $$220 \mathrm{~V}$$ dc Why?
What should be the inductance of an inductor connected to $$200 \mathrm{~V}, 50 \mathrm{~Hz}$$ source so that the maximum current of $$\sqrt{2}$$ A flows through it?
During the phenomenon of resonance
A DC ammeter and a hot wire ammeter are connected to a circuit in series. When a direct current is passed through circuit, the DC ammeter shows 6 A. When AC current flows through circuit, what is the average readings in DC ammeter and the AC ammeter, if DC and AC currents flows simultaneously through the circuit?
A series L-C-R circuit is connected to an AC source of 220 V and 50 Hz shown in figure. If the readings of the three voltmeters $$V_1,V_2$$ and $$V_3$$ are 65 V, 415 V and 204 V respectively, the value of inductance and capacitance will be
An alternating voltage = 200 $$\sin 100t$$ is applied to a series combination of $$R=30\Omega$$ and an inductor of 400 mH. The power factor of the circuit is,
The AC voltage across a resistance can be measured using a
The formula of capacitative reactance is
For the same resonant frequency, if L is changed from L to $${L \over 3}$$, then capacitance should change from C to
What should be the value of self-inductance of an inductor that should be connected to 220 V 50 Hz supply, so that a maximum current of 0.9 A flows through it?
If impedance is $$\sqrt3$$ times of resistance, then find phase difference.
For a series L-C-R circuit at resonance, which statement is not true?