TENSION FOR A CONSTANT FREQUENCY USING SONOMETER AIM To study the relationship between the length of a given wire and tension for constant frequency using a sonometer APPARATUS REQUIRED Sonometer, tuning fork of known frequency, meter scale, rubber pad, paper rider, hanger with half – kilogram masses, wooden bridges. FORMULA The frequency of the fundamental mode of vibration of a string is given by, n l = Hz If n is a constant, for a given wire ( m is constant) l is constant. where n → Frequency of the fundamental mode of vibration of a string ( Hz ) m → Mass per unit length of string ( kg m – ) T → Tension in the string (including the mass of the hanger) = Mg (N) l → Length of the string between the wedges (metre) M → Mass suspended, including the mass of the hanger (kg) DIAGRAM STUDY OF RELATION BETWEEN LENGTH OF THE GIVEN WIRE AND TENSION FOR A CONSTANT FREQUENCY USING SONOMETER Wedge Steel wire Mass hanger Load UNIT- (XI- - ) PRACTICAL FIRST UNIT- (XI- - ) PRACTICAL FIRST - - - - Practical PROCEDURE ¾ Set up the sonometer on the table and clean the groove on the pulley to ensure that it has minimum friction. ¾ Keep a small paper rider on the wire,between the bridges.
¾ Place a mass of kg for initial reading in the mass hanger. ¾ Now, strike the tuning fork and place its shank stem on the bridge A and then slowly adjust the position of the bridge B till the paper rider is agitated violently and might eventually fall due to resonance. ¾ Measure the length of the wire between wedges at A and B which is the fundamental mode corresponding to the frequency of the tuning fork. ¾ Increase the load on the hanger in steps of .
kg and each time find the resonating length as done before with the same tuning fork. ¾ Record the observations in the tabular column.