3B Scientific Pohl's Torsion Pendulum - Manual

6
Operating instructions
3B SCIENTIFIC 3B SCIENTIFIC 3B SCIENTIFIC 3B SCIENTIFIC 3B SCIENTIFIC® PHYSICS PHYSICS PHYSICS PHYSICS PHYSICS
The torsion pendulum may be used to investigate free,
forced and chaotic oscillations with various degrees of
damping.
Experiment topics:
• Free rotary oscillations at various degrees of damp-
ing (oscillations with light damping, aperiodic os-
cillation and aperiodic limit)
• Forced rotary oscillations and their resonance
curves at various degrees of damping
• Phase displacement between the exciter and reso-
nator during resonance
• Chaotic rotary oscillations
• Static determination of the direction variable D
• Dynamic determination of the moment of inertia J
1. Safety instructions
• When removing the torsional pendulum from the
packaging do not touch the scale ring. This could
U15040 Torsion pendulum according to Professor Pohl
12/03 ALF
1
2
3
4
5
6
7
8
lead to damage. Always remove using the handles
provided in the internal packaging.
• When carrying the torsional pendulum always hold
it by the base plate.
• Never exceed the maximum permissible supply
voltage for the exciter motor (24 V DC).
• Do not subject the torsional pendulum to any un-
necessary mechanical stress.
2. Description, technical data
The Professor Pohl torsional pendulum consists of a
wooden base plate with an oscillating system and an
electric motor mounted on top. The oscillating system
is a ball-bearing mounted copper wheel (5), which is
connected to the exciter rod via a coil spring (6) that
provides the restoring torque. A DC motor with coarse
and fine speed adjustment is used to excite the tor-
sional pendulum. Excitement is brought about via an
eccentric wheel (14) with connecting rod (13) which
1 Exciter motor
2 Control knob for fine adjustment of the exciter voltage
3 Control knob for coarse adjustment of the exciter voltage
4 Scale ring
5 Pendulum body
6 Coil spring
7 Pointer for the exciter phase angle
8 Pointer for the pendulum’s phase angle
9 Pointer for the pendulum’s deflection
bl Exciter
bm Eddy current brake
bn Guide slot and screw to set the exciter amplitude
bo Connecting rod
bp Eccentric drive wheel
bq 4-mm safety socket for exciter voltage measurement
br 4-mm safety sockets for the exciter motor power supply
bs 4-mm safety sockets for the eddy current brake power
supply
9
bl bm bn bo bp
bq br bs