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A.C.Sonometer: Every object has a natural frequency of vibration.
If kinetic energy is applied to an object at a rate that matches its natural frequency,
resonance occurs and the object vibrates. Here, we use an A.C.Sonometer to find the
frequency of vibration. An A.C sonometer is an apparatus by which
the transverse vibrations of strings can be studied. On the box are two fixed bridges,
near the ends, and at one end is a pulley. A string, often a steel wire, is fastened
at one end, run over the bridges and the pulley, and attached to a weight holder hanging below
the pulley. Weights can be added to the holder to produce tension in the wire, and a third,
movable bridge, can be placed under it to change the length of the vibrating section
of the string. Procedure:
In this experiment a small current, produced by a signal generator, causes the sonometer
wire to move up and down due to interaction with the magnetic field of a U-shaped magnet.
When the rate of movement due to the current matches the fundamental frequency of the wire,
resonance occurs causing noticeable vibration. If the tension on the wire is increased (length
kept constant), the resonant frequency of the wire also increases.