LC Oscillations

IMPORTANT

LC Oscillations: Overview

This topic covers concepts such as L-C Oscillator Circuit, Comparison of L-C Oscillations with Spring Block Oscillations, Frequency of L-C Oscillator Circuit, Comparison between Self Inductance and Inertia, etc.

Important Questions on LC Oscillations

EASY
IMPORTANT

The current through a coil of self-inductance L=2mH is given by i=t2e-t at time t. How long it will take to make the emf zero?

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IMPORTANT

When current in coil changes from 5 A to 2 A in 0.1 s, an average of 50 V is produced. The self-inductance in HenryH of the coil is n3. Write the value of n.

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What is LC oscillation?

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A circuit consists of a coil with inductance L and an uncharged capacitor of capacitance C. The coil is in a constant uniform magnetic field such that the flux through the coil is ϕ. At time t=0 min, the magnetic field is abruptly switched OFF. Let ω0=1LC and ignore the resistance of the circuit. Then,

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IMPORTANT

A 60μF capacitor is charged to 100 volts. This charged capacitor is connected across a 1.5mH coil, so that LC oscillations occur. The maximum current in the coil is:-

MEDIUM
IMPORTANT

In an LC circuit shown in figure, C=2 F and L=2 H. At time t=0, charge on the capacitor is 3 coulomb and it is decreasing with rate of 4 C s-1. Then choose the correct statement.

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For the circuit shown in the figure, the current through the inductor is 0.6 A, while the current through the capacitor is 0.4 A. The current drawn from the generator is:

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The natural frequency of the circuit is (in rad s-1),

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IMPORTANT

In an LC oscillator circuit L = 10 mH, C = 40µF. If initially at t = 0 the capacitor is fully charged with 4µC then find the current in the circuit when the capacitor and inductor share equal energies. 

HARD
IMPORTANT

The diagram shows a capacitor C and a resistor R connected in series to an AC source, V1 and V2 are voltmeters and A is an ammeter. Consider now the following statements :

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(I) Readings in A and V1 are always in phase

(II) Readings in A and V2 are always in phase

(III) Reading in V1 is ahead with reading in V2

Which of these statements are is correct : 

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IMPORTANT

The switch in the circuit pictured is in position a for a long time. At t = 0 the switch is moved from a to b. The current through the inductor will reach its first maximum after moving the switch in a time : -

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Initially, the key was placed on 1 till the capacitor got fully charged. Now the key is placed on 2 at t=0. The minimum time when the energy in both capacitor and inductor will be the same.

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A charged 30 μF capacitor is connected to a 27 mH inductor. The angular frequency of free oscillations of the circuit is

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How oscillations are produced using inductor and capacitor?

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A 1.5μF capacitor is charged to 60V and a15mH coil is connected across it. Assuming that the circuit contains no resistance, what will be the maximum current in the coil?

HARD
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An inductor and two capacitors are connected in the circuit as shown in figure. Initially capacitor A has no charge and capacitor B has CV charge. Assume that the circuit has no resistance at all. At t=0, switch S is closed, then given  LC=2π2×104s2 & CV=100 mC
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MEDIUM
IMPORTANT

A 1.5 μF capacitor is charged to 60 V. The charging battery is then disconnected and a 15 mH coil is connected in series with the capacitor so that LC oscillations occur. Assuming that the circuit contains no resistance, the maximum current in this coil shall be close to

MEDIUM
IMPORTANT

An LC circuit contains a 20 mH inductor and a 50 μF capacitor with an initial charge of 10 mC. The resistance of the circuit is negligible. Let the instant at which the circuit which is closed be t=0. At what time the energy stored is completely magnetic?

HARD
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A circuit has a self inductance of 1 henry and carries a current of 2 A. To prevent sparking when the circuit is broken, a capacitor which can withstand 400 volts is used. The least capacitance of the capacitor connected across the switch must be equal to

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IMPORTANT

The natural frequency of an LC circuit is 125 kHz. When the capacitor is totally filled with a dielectric material, the natural frequency decreases by 25 kHz. Dielectric constant of the material is nearly