In the surface tension experiment, the pull-off force / surface tension of liquids, as well as the buoyancy force and the surface free energy, are discussed.
For this purpose, the force acting on an aluminum ring with a cutting edge is determined when the ring moves uniformly through the liquid and when the ring is pulled out of the liquid.
Both, the position of the ring and the force acting on the ring are measured simultaneously. This is realized via the PS400 Remote Controlled Positioning System (1023414) and a force sensor (1021676). The digital data is automatically processed and visualized in the Coach7 software, so that the force changes are graphically displayed when the ring is pulled out of the liquid.
The distances between different 'force plateaus' can then be used to determine the pull-off force / surface tension and the buoyancy force.
Advantages when using the PS400 Remote Controlled Positioning System (article no.1023414):
With the positioning system, the ring is pulled out at a slow and constant speed, which is essential for the determination of pull-off forces. In addition, it ensures the reproducibility of the measurement.
Advantages of computer-aided experimentation:
Besides the advantage of instantaneous visualization of the measurement, the measurement is also very fast (< 1 min). Therefore, varying the test conditions (e.g. different liquids or additives to liquids) is easy and quick to implement.
Liquids used:
The experiment can be carried out very easily with water as a liquid medium. However, one can also add additives to the water (e.g. dishwashing detergent) in order to analyze the effect on the surface tension. The use of liquids with higher or lower viscosity than water is also possible. In this case, however, one must comply with the local safety guidelines (safety data sheet).
Variants of digital data processing:
Variant 1: (PC/Tablet)
2 x
1021514
Sensor Cable
1 x
1022284
WiLab
1 x
Software License Coach7
or
Variant 2: (Data-Logger VinciLab)
2 x
1021514
Sensor Cable
1 x
1021477
VinciLab
1 x
Software License Coach7
Note: Alternatively, the position of the carriage of the positioning system can be read out with the output voltage VOut. Thus, monitoring systems or software of other suppliers can acquire the position information by using a suitable voltage sensor.