List of top Physics Questions on KCL/ KVL in AC Circuits

A series LCR circuit is connected to an alternating source of emf \( E \). The current amplitude at resonance frequency is \( I_0 \). If the value of resistance \( R \) becomes twice of its initial value, then amplitude of current at resonance will be:
A capacitor and an inductor are connected in series across an ac source of voltage of variable frequency. The frequency is increased continuously. The nature of the circuit before and after the resonance will be:
Plot a graph to show the variation of reactance of the element with the frequency of the applied voltage.
An ac source of voltage \( V = V_0 \sin \omega t \) is connected to a circuit element \( X \). It is observed that the current flowing through \( X \) varies as \( I = I_0 \sin\left(\omega t - \frac{\pi}{2}\right) \).
(a) Identify the element \( X \) and write the expression for its reactance.
In an a.c. circuit, voltage and current are given by:\[V = 100 \sin (100 \, t) \, \text{V}\]and\[I = 100 \sin \left(100 \, t + \frac{\pi}{3}\right) \, \text{mA}\]respectively. The average power dissipated in one cycle is:
Establish the expression for impedance of the circuit when elements X, Y, and Z are connected in series to an AC source. Show the variation of current in the circuit with the frequency of the applied AC source.
You are given three circuit elements X, Y, and Z. They are connected one by one across a given ac source. It is found that \( V \) and \( I \) are in phase for element X. \( V \) leads \( I \) by \( \frac{\pi}{4} \) for element Y while \( I \) leads \( V \) by \( \frac{\pi}{4} \) for element Z. Identify elements X, Y, and Z.
Two long straight thin wires AB and CD have linear charge densities \( 10 \, \text{mC/m} \) and \( -20 \, \text{mC/m} \), respectively. They are kept parallel to each other at a distance of 1 m. Find the magnitude and direction of the net electric field at a point midway between them.
What is meant by the transformation ratio of a transformer? In a step-down transformer, the transmission line voltage of 2200 volt is changed to 220 volt. Number of turns in the primary coil is 5000. The efficiency of the transformer is 90 percent and output power is 8kW.

What is Lenz’s law?