We report on the construction of a simple apparatus for measuring the small overpressure inside soap bubbles with sizes in the cm range. The apparatus uses Archimedes' principle and it can be easily calibrated. Thus, surface tensions of soap films can be measured quantitatively. The apparatus is also well suited to demonstrate the Young–Laplace law in front of an audience such as a classroom. The design of the apparatus is subject to a criterion for stability, which we discuss in detail and that can be discussed with the audience. The setup of the apparatus requires components that are commonly available in households or school labs and it can be set up by students on their own.
References
1.
David
Lovett
, Demonstrating Science with Soap Films
(Institute of Physics Publishing
, Bristol and Philadelphia
, 1994
).2.
F.
Behroozi
, H. K.
Macomber
, J. A.
Dostal
, C. H.
Behroozi
, and B. K.
Lambert
, “The profile of a dew drop
,” Am. J. Phys.
64
(9
), 1120
–1125
(1996
).3.
J.
Pellicer
, J. A.
Manzanares
, and S.
Mafe
, “The physical description of elementary surface phenomena—Thermodynamics versus mechanics
,” Am. J. Phys.
63
(6
), 542
–547
(1995
).4.
Phywe Systeme Gmbh & Co. KG
(D37079 Göttingen, Germany), model 03091.00.5.
F. L.
Roman
, J.
Faro
, and S.
Velasco
, “A simple experiment for measuring the surface tension of soap solutions
,” Am. J. Phys.
69
(8
), 920
–921
(2001
).6.
F.
Behroozi
and P. S.
Behroozi
, “Determination of surface tension from the measurement of internal pressure of mini soap bubbles
,” Am. J. Phys.
79
(11
), 1089
–1093
(2011
).7.
T.
Thomas Dorfmüller
, Wilhelm T.
Hering
, Klaus
Stierstadt
, and Günther
Fischer
, Bergmann Schaefer: Lehrbuch der Experimentalphysik
, 11th ed. (Walter de Gruyter
, Berlin
, 1998
), Vol. 1
.© 2019 American Association of Physics Teachers.
2019
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