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 Aim: to find the Relation between the Tension is a wire and its Fundamental Frequency of Resonance See Resonance of a String under Tension, Measuring the Strength of a Magnetic Field Method The method suggested here involves passing a variable frequency alternating current through a wire (under tension) placed at 90° to a magnetic field. Set up apparatus something like that shown below. The signal generator might need an amplifier as it must be capable of supplying enough current to cause visible oscillations of the wire. Find the fundamental frequency of resonance for as wide a range of tensions as the wire can support. Assuming that the pulley is frictionless, the tension in the wire is equal to the weight of the hanging mass. The calibration of many signal generators is approximate. Use a frequency meter to measure the frequencies supplied by the generator. A frequency meter is connected in the same way as a voltmeter. The relation between frequency and tension should be verified by plotting a suitable graph. If you have enough time try to cause the wire to oscillate at one (or more) of its higher harmonics. To see, for example, the second harmonic, you should change the position of the magnet... If a strobe light is available, it is amusing to observe the oscillations with the strobe set to the same (or very nearly the same) frequency as the oscillations.

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