The alternating current supply is a convenient source of current in frequency measurements and comparisons, unless high degree of constancy is desired. An ac arc also is a fairly satisfactory intermittent source of light. A number of experiments are described, making use of these facts:
- (1) The motion of a tuning fork and explanation of beats.
- (2) Waves on liquids can be shown, including the case of beats.
- (3) Slight phase changes may be shown when a heavy motor is connected to the line.
- (4) An audio-oscillator may be calibrated.
- (5) Reaction of closely and loosely coupled circuits may be mechanically demonstrated; and an explanation found for the difficulties sometimes encountered in Melde’s Experiment. Also, there are explained two useful theorems in connection with Lissajou figures.
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