P1.5.3.2 Torsion Pendulum (Stop Clock)
Overview
Free rotational oscillations- measuring with a hand held stop clock.
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Description
The torsion pendulum after Pohl can be used to investigate free or forced harmonic rotational oscillations. An electromagnetic eddy current brake damps these oscillations to a greater or lesser extent, depending on the set current. The torsion pendulum is excited to forced oscillations by means of a motor-driven eccentric rod. The aim of the first experiment is to investigate free harmonic rotational oscillations of the type
f(t) = f0 · cosvt · e–d · t where v = öv2 0 – d2
v0: characteristic frequency of torsion pendulum
To distinguish between oscillation and creepage, the damping constant F is varied to find the current I0 which corresponds to the aperiodic limiting case. In the oscillation case, the angular frequency v is determined for various damping levels from the oscillation period T and the damping constant d by means of the ratio fn +1 = e– d · T fn 2 of two sequential oscillation amplitudes. Using the relationship
v2 = v20 – d2 we can determine the characteristic frequency v0.
In the next experiment (P1.5.3.3), the torsion pendulum is excited to oscillations with the frequency v by means of a harmonically variable angular momentum. To illustrate the resonance behavior, the oscillation amplitudes determined for various damping levels are plotted as a function of v2 and compared with the theoretical curve f0 =M0 ·1I ö(v2 – v20)2 + d2 · v2 I: moment of inertia of torsion pendulum
Cat. No. Description Quantity
346 00 Torsion pendulum 1
562 793 Plug-in power supply for torsion pendulum 1
521 545 DC power supply 0 … 16 V, 5 A 1
531 120 Amperemeter, DC, I �n2 A, e.g. Multimeter LD analog 20 1
531 120 Voltmeter, DC, U �n24 V, e. g. Multimeter LD analog 20 1
313 07 Stopclock I 30 s/15 min 1
500 442 Connection lead, 100 cm, blue 1
501 46 Pair of cables, 1 m, red and blue 2
f(t) = f0 · cosvt · e–d · t where v = öv2 0 – d2
v0: characteristic frequency of torsion pendulum
To distinguish between oscillation and creepage, the damping constant F is varied to find the current I0 which corresponds to the aperiodic limiting case. In the oscillation case, the angular frequency v is determined for various damping levels from the oscillation period T and the damping constant d by means of the ratio fn +1 = e– d · T fn 2 of two sequential oscillation amplitudes. Using the relationship
v2 = v20 – d2 we can determine the characteristic frequency v0.
In the next experiment (P1.5.3.3), the torsion pendulum is excited to oscillations with the frequency v by means of a harmonically variable angular momentum. To illustrate the resonance behavior, the oscillation amplitudes determined for various damping levels are plotted as a function of v2 and compared with the theoretical curve f0 =M0 ·1I ö(v2 – v20)2 + d2 · v2 I: moment of inertia of torsion pendulum
Cat. No. Description Quantity
346 00 Torsion pendulum 1
562 793 Plug-in power supply for torsion pendulum 1
521 545 DC power supply 0 … 16 V, 5 A 1
531 120 Amperemeter, DC, I �n2 A, e.g. Multimeter LD analog 20 1
531 120 Voltmeter, DC, U �n24 V, e. g. Multimeter LD analog 20 1
313 07 Stopclock I 30 s/15 min 1
500 442 Connection lead, 100 cm, blue 1
501 46 Pair of cables, 1 m, red and blue 2
; "P1.5.3.2 Torsion Pendulum (Stop Clock)")