Demonstration of Low-Frequency Electrical Oscillations

An underdamped LCR circuit has been constructed which has an oscillatory period in the region of 0.5 to 5 sec. The current and emf in the circuit are measured by means of a galvanometer. The time behavior of the circuit is studied by means of a light beam chopper and sampling technique. A simple rotating magnet mechanical-electrical power pump is used to study the frequency response of the circuit for different time periods and damping conditions. A low-frequency sinusoidal electrical oscillator is used to study the response curve of the galvanometer and the behavior of the LCR circuit with series coupling. The potential of the galvanometer for quantitative measurements of the time varying systems $(T>0.5 sec)$ has been established. The experiment is instructive and can be used for introductory as well as advanced courses.