Torsion pendulum after Pohl

Function and Applications

To investigate forced and free oscillations under different damping conditions.

Examples of experiments:

determination of the frequency of a damped oscillation, representation of sequential amplitudes of a damped oscillation (log. decrement), non periodical or crawling adjustment to the zero position for correspondingly adjusted damping, forced oscillations and their resonance graphs for different damping conditions, phase shift between exciter and resonator in the resonance case.

Benefits

• Copper wheel held on ball bearings which acts as an oscillating system (resonator).
• Periodic excitation through high sensitivity adjustment direct current gearing motor which acts on the exterior end of a spiral spring by means of an excenter and a lever.
• The other end of the spiral spring is attached to the axle of the resonator.
• Two potentiometers for coarse and fine adjustment of the motor; two pairs of 4 mm jacks for power supply of the motor and of the eddy current brake; pair of 4 mm jacks for direct connection of a voltmeter to the motor.
• Exciter and resonator have pointers; ring scale with slots for shadow projection; damping of the oscillating system through electromagnetic eddy current brake.

Equipment and Technical Data

• Eigenfrequency approx. 0.5 Hz
• excitation frequency 0…1.3 Hz
• continuously adjustable
• connections motor and rotation adjusting unit max. 24 V DC, 650 mA
• eddy current brake 0…20 V DC, max. 2A
• dimensions: base plate (mm)140×430
• scale d = 300 mm