Alternating Current - Electromagnetism - Physics Previous Year Questions

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

If impedance is \(\sqrt3\) times of resistance, then find phase difference.

For the same resonant frequency, if L is changed from L to \({L \over 3}\), then capacitance should change from C to

The formula of capacitative reactance is

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?

During the phenomenon of resonance

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,

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

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?

The AC voltage across a resistance can be measured using a

\(220 \mathrm{~V}\) 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?

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

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 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

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 \(\mathrm{A}\).

When an A.C. source is connected to a inductive circuit,

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?

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:

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 :