Determination of frequency of A.C. by Melde's Apparatus || Physics Practical || FSC Part 1 ||

Episode Overview

• This video provides a comprehensive guide to a physics experiment for determining the frequency of an AC power supply using Melde's apparatus.
• It begins by identifying and explaining each piece of equipment required, from the meter rule and pulley to the electronic vibrator setup.
• The episode walks through the detailed, step-by-step procedure for setting up the apparatus, generating standing waves on a string, and taking accurate measurements.
• It concludes by showcasing the observation and calculation table, deriving the final frequency value, and listing essential precautions for conducting the experiment successfully.

Key Concepts

• Melde's Apparatus: The core experimental setup, which uses an electromagnet to drive a steel vibrator, creating oscillations in a stretched string. It's also referred to as an electric sonometer.
• Standing Waves: The experiment is based on the principle of generating standing waves, which are formed by the superposition of a wave and its reflection. These waves have stationary points called nodes and points of maximum amplitude called anti-nodes.
• Relationship between Frequency, Tension, and Linear Mass Density: The experiment's goal is to use the relationship between the frequency of vibration (f), the number of loops (n), the length of the string (L), the tension in the string (T), and its mass per unit length (m) to calculate the unknown frequency of the AC source.
• Experimental Variables: Key variables that are measured or controlled include the mass in the pan (which determines tension), the distance between extreme nodes (L), and the number of loops formed on the string.

Quotes

• At 00:08 - "Experiment: Determination of frequency of A.C. by Melde's apparatus / electric sonometer." - This slide clearly states the objective of the entire experimental demonstration.
• At 01:27 - "4: Adjust the distance of the pulley from the vibrator along with weights, such that well defined loop are formed in the string." - This on-screen text outlines the critical step in the procedure for achieving a clear standing wave pattern for measurement.
• At 03:33 - "Mean value of f = (47.7+48.7+49.2)/3 = 48.5 Hz" - This slide presents the final calculation, showing how multiple readings are averaged to determine the experimental value for the AC frequency.

Takeaways

• To achieve a clear standing wave, you must carefully adjust both the tension (by changing the weights) and the length of the string (by moving the pulley) until stable, well-defined loops are visible.
• The accuracy of the result depends heavily on precise measurements, particularly the length between the extreme nodes (L) and the mass per unit length of the thread.
• This experiment provides a practical method to determine an electrical property (AC frequency) by observing and measuring purely mechanical phenomena (wave properties on a string).