. Physical laboratory experiments : mechanics, optics and heat. n a sine curve,each wave of which rep-resents a known intervalof time. The time be-tween two events isfound by counting the number of vibrations and fractions ofa vibration of the fork between the corresponding dots. Theresult is independent of the velocity of rotation of the drum,a greater velocity serving merely to draw out the waves toa greater extent, but in no way altering their number. It isconvenient to have the fork driven electrically by a smallelectromagnet placed between the prongs and run on anindependent battery circu
. Physical laboratory experiments : mechanics, optics and heat. n a sine curve,each wave of which rep-resents a known intervalof time. The time be-tween two events isfound by counting the number of vibrations and fractions ofa vibration of the fork between the corresponding dots. Theresult is independent of the velocity of rotation of the drum,a greater velocity serving merely to draw out the waves toa greater extent, but in no way altering their number. It isconvenient to have the fork driven electrically by a smallelectromagnet placed between the prongs and run on anindependent battery circuit, as shown in Fig. 31. Theamplitude of vibration may thus be maintained constant andvigorous for any length of time. The trap B (Fig. 30), consists of a flat strip of iron A(Fig. 32), hinged at one end and held up horizontally in thepath of the falling ball by a strong permanent magnet current passes across from B through A to C, so thatthe instant the ball falls upon A the circuit is broken. Theelectrical connections will be easily seen from Fig. Fig. 32. LAW OF FREELY FALLING BODIES 111 When the circuit through the electromagnet is closed, thecurrent passes from the positive terminal of the storage bat-tery to 1, a, A, a, C, back to the negative terminal. Onthrowing the jack-knife switch from 1 to 2, the circuit isbroken, but instantly afterward closed again through thetrap B, the current then passing from the positive terminalto 2, h, up the metallic rail / to B, across the trap to theother rail r down to h, a, C, and so back to the negativeterminal. Procedure.—Preparation of lampblack cylinder.—Fastena sheet of the special chronograph paper tightly over thedrum. See that the edges of the paper overlap in such amanner that on rotating the drum the style passes from theupper to the under, otherwise it is likely to catch and spoilthe record. Hold a piece of burning camphor in the spoonprovided close under the cylinder, and revolve the cylinderback and forth ov
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Keywords: ., bookcentury1900, bookde, booksubjectmechanics, booksubjectphysics
