Alternating Current PYQs

An AC circuit contains a resistance of 1 kΩ, a capacitor of 0.1 μF and an inductor of 1 mH connected in series. The resonance frequency of the circuit is approximately:

The peak value of an alternating current is 5 A and frequency is 60 Hz. How long will the current, starting from zero, take to reach the peak value?

To an ac power supply of 220 V at 50 Hz, a resistor of 20 Ω, a capacitor of reactance 25 Ω and an inductor of reactance 45 Ω are connected in series. The corresponding current in the circuit and the phase angle between the current and the voltage is respectively -

In an ideal transformer, the turns ratio is N$_p$/N$_s$ = 1/2. The ratio V$_s$ : V$_p$ is equal to (the symbols carry their usual meaning):

A 10 μF capacitor is connected to a 210 V, 50 Hz source as shown in figure. The peak current in the circuit is nearly (Take π = 3.14):

A 12 V, 60 W lamp is connected to the secondary of a step down transformer, whose primary is connected to mains of 220 V. Assuming the transformer to be ideal, what is the current in the primary winding?

In a series LCR circuit, the inductance L is 10 mH, capacitance C is 1 μF and resistance R is 100 Ω. The frequency at which resonance occurs is :

The net impedance of circuit (as shown in figure) will be :

The peak voltage of the AC source is equal to:

A series LCR circuit with inductance 10 H, capacitance 10 μF, resistance 50 Ω is connected to an AC source of voltage V = 200 sin(100t) volt. If the resonance frequency of the LCR circuit is ν₀ and the frequency of AC source is ν, then:

A step down transformer connected to AC mains supply of 220 V is made to operate at 11 V, 44 W lamp. Ignoring power losses in the transformer, what is the current in the primary circuit?

A series LCR circuit containing 5.0 H inductor, 80 μF capacitor and 40 Ω resistor is connected to 230 V variable frequency AC source. The angular frequencies of the source at which power transferred to the circuit is half the power at resonance are likely to be

A 40 $\mu$F capacitor is connected to a 200 V, 50 Hz AC supply. The rms value of the current in the circuit is nearly:

A series LCR circuit is connected to an ac voltage source. When L is removed from the circuit, the phase difference between current and voltage is π/3. If instead C is removed from the circuit, the phase difference is again π/3 between current and voltage. The power factor of the circuit is :

The variation of EMF with time for four types of generators are shown in the figures. Which amongst them can be called AC?

An inductor 20 mH, a capacitor 100 μF and a resistor 50 Ω are connected in series across a source of emf, V = 10 sin 314t. The power loss in the circuit is:

Which of the following combinations should be selected for better tuning of an L-C-R circuit used for communication?

The potential differences across the resistance, capacitance and inductance are $80\ \text{V}$, $40\ \text{V}$ and $100\ \text{V}$ respectively in an L-C-R circuit. The power factor of this circuit is:

A series R-C circuit is connected to an alternating voltage source. Consider two situations: (a) When the capacitor is air filled. (b) When the capacitor is mica filled. Current through the resistor is $i$ and voltage across the capacitor is $V$. Then:

A transformer having efficiency of 90% is working on 200 V and 3 kW power supply. If the current in the secondary coil is 6A, the voltage across the secondary coil and the current in the primary coil are respectively:

A coil of self-inductance $L$ is connected in series with a bulb $B$ and an AC source. Brightness of the bulb decreases when

The instantaneous values of alternating current and voltage in a circuit are given as $$i=\frac{1}{\sqrt{2}}\sin(100\pi t)\,\text{A}$$ and $$e=\frac{1}{\sqrt{2}}\sin\left(100\pi t+\frac{\pi}{3}\right)\,\text{V}$$. The average power consumed in the circuit is:

The r.m.s. value of potential difference V shown in the figure is:

A coil has resistance 30 ohm and inductive reactance 20 ohm at 50 Hz frequency. If an ac source of 200 volt, 100 Hz, is connected across the coil, the current in the circuit will be:

Power dissipated in an LCR series circuit connected to an AC source of emf $\varepsilon$ is:

In an a.c. circuit the e.m.f. (e) and the current (i) at any instant are given respectively by e = E₀ sin ωt and i = I₀ sin(ωt − φ). The average power in the circuit over one cycle of a.c. is

The core of a transformer is laminated because:

A coil of inductive reactance 31 Ω has a resistance of 8 Ω. It is placed in series with a condenser of capacitive reactance 25 Ω. The combination is connected to an a.c. source of 110 V. The power factor of the circuit is:

In a circuit, $L$, $C$ and $R$ are connected in series with an alternating voltage source of frequency $f$. The current leads the voltage by $45^\circ$. The value of $C$ is: