A device for measuring the surface tension coefficient of liquid based on standing wave vibration

Abstract

The present invention discloses a device for measuring the surface tension coefficient of a liquid based on standing wave vibration, which includes a vibration generator (capable of precisely regulating the output frequency and amplitude), a string support platform (equipped with a standard meter ruler), a fixed pulley, a weight pan and weights, a measuring hanging ring, a water-containing container, a fine screw lifting table, and a CCD camera. The present invention does not need to measure the force when the hanging ring is pulled off, but only needs to measure the position change of the standing wave nodes before and after the water film breaks, so as to calculate the surface tension coefficient of the liquid. It has good measurement stability, high precision, simple operation, intuitive phenomenon, and can be used as a teaching instrument for physical experiments in colleges and universities.

Description

Technical Field

[0001] The present invention relates to the technical field of measuring the surface tension coefficient of a liquid, and specifically relates to a device for measuring the surface tension coefficient of a liquid based on standing wave vibration Background Art

[0002] In college physics experiments, the pulling-off method is generally used to measure the surface tension coefficient of a liquid. A force-sensitive element is used to measure the surface tension, and the error is greatly affected by the accuracy of the force-sensitive element. At the same time, since the pulling forces before and after the liquid film is broken are measured, the naked-eye reading is inaccurate, which will also affect the experimental error Summary of the Invention

[0003] In view of the problem that the pulling-off method for measuring surface tension is not accurate enough, the present invention proposes a new method for measuring the surface tension coefficient, which can improve the measurement accuracy

[0004] To this end, the present invention adopts the following technical solutions

[0005] A method for measuring the surface tension of a liquid based on a standing wave experiment instrument. Let the vibration frequency be v and the linear density be ρ. The generated standing wave satisfies the wave equation. From the wave velocity The wavelength λ = μ / v, that is, T = λ 2 v 2 ρ, where T is the tension on the string

[0006] For the standing wave of the string, the relationship between the string length L and the wavelength λ is: λ = 2L / n, n = 1, 2, 3......, n is the number of wave antinodes. So T = 4v 2 ρL 2 / n 2 , so the change in the tension on the string is converted into the movement of the standing wave node

[0007] For the surface tension coefficient, when measured by the pulling-off method, the difference in the tension of the string before and after the water film breaks is the surface tension of water: T 断前 -T 断后 = f = απ(D 1 +D 2 ), the inner diameter and outer diameter of the hanging ring used for measurement are D 1 and D 2 , so the surface tension coefficient is α = (T 断前 -T 断后 ) / π(D 1 +D 2 )

[0008] Use the standing wave experiment table to generate a standing wave. Set the coordinate of the tangent position of the pulley and the string as x 0 , for a certain fixed frequency v, select the distance x 0Take the nth node at [specific location] as the research object, and record the coordinate positions x 1 and x 2 of this node before and after the moment when the water film breaks. Use a high-speed camera and video analysis tool to accurately find the coordinate position of this node. Then the chord length corresponding to the n nodes is: Before breaking, L = x 0 - x 1 , and after breaking, L = x 0 - x 2 .

[0009] Finally, the surface tension coefficient is calculated by the formula . BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 is a schematic structural diagram of the present invention;

[0011] Figure 2 is a top view of the chord support platform.

[0012] In the figure: 1. CCD camera, 2. Chord support platform, 3. Vibration generator, 4. Scale, 5. Fixed pulley, 6. Chord, 7. Weighing platform with weights, 8. Hanging ring, 9. Water container, 10. Fine screw lifting table. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0013] The present invention will be further described in detail below with reference to the drawings and specific embodiments.

[0014] As shown in Figure 1 , a device for measuring the surface tension coefficient of a liquid based on standing wave vibration includes a vibration generator (which can precisely control the output frequency and amplitude), a chord support platform (equipped with a standard meter scale), a fixed pulley, a weight pan and weights, a measuring hanging ring, a water container, a fine screw lifting table, and a CCD camera. Ensure that the chord is horizontal and parallel to the scale direction of the meter scale, and the rotation of the fixed pulley is as frictionless as possible.

[0015] In this experiment, pure water is used as the liquid to be measured.

[0016] Step 1: Measure the inner and outer diameters D 1 = 32.96 mm and D 2 = 35.10 mm of the hanging ring 8. Measure the linear density of the chord 6 as ρ = 0.35×10 -3 kg / m.

[0017] Step 2: Hang the clean hanging ring on the hook at the free end of the chord, adjust the hanging ring to be horizontal, and add an appropriate amount of weights 7 to straighten the chord. Turn on the standing wave generator 3 and adjust the appropriate output frequency and amplitude. The frequency in this experiment is 55.5 Hz. Make 3 - 4 stable and obvious standing wave waveforms appear on the chord. Except for the vibration source, record the position of the node closest to the vibration source. As shown inFigure 2 As shown, the number of antinodes n between the wave node and the fixed pulley is 3.

[0018] Step 3: Adjust the lifting platform 10 to keep the string stable. Slowly raise the liquid level. When the lower edge part of the hanging ring is completely immersed in the liquid level, slowly lower the liquid level, and at the same time use the CCD camera 1 to record the change in the position of the wave node closest to the vibration source.

[0019] Step 4: Observe frame by frame with a video processing tool and read out the positions x of the wave nodes before and after the liquid film breaks. 1 = 20.0 cm and x 2 = 21.0 cm.

[0020] Step 5: Combine the position x of the fixed pulley 0 = 106.5 cm, and calculate the surface tension coefficient according to the formula as

[0021]

[0022] Step 6: The experimental temperature is 21 °C, and the theoretical value of the surface tension coefficient of water at this temperature is 72.28×10 -3 N / m. The error between the measured value and the theoretical value in this experiment is only 0.38%.

[0023] The above are only the preferred embodiments of the present invention, and it is not intended to limit the present invention in any other form. Any modification or equivalent change made according to the technical essence of the present invention still belongs to the scope protected by the present invention.

Claims

1. A measuring device for the surface tension coefficient of a liquid based on standing wave vibration, which consists of a vibration generator, a string, a string support platform, a fixed pulley, a weight pan and weights, a measuring ring, a water container, a fine screw lift, and a CCD camera; It is characterized in that, One end of the string is fixed on the vibration generator, and the other end is suspended with weights and a ring through a fixed pulley to tighten the string. The vibration generator generates vibrations with a certain frequency and amplitude, and stable standing waves are formed at both ends of the string and the appropriate node positions are found. The ring is immersed in the liquid to be measured, and then the liquid level is slowly lowered. During the process of pulling out the liquid film by the ring, the corresponding positions of the node before and after the liquid film breaks are measured, so that the surface tension coefficient can be calculated; According to the wave equation, the tension T on the string is T = λ 2 v 2 ρ = 4v 2 ρL 2 / n 2 , where λ is the wavelength of the standing wave, v is the frequency of the standing wave, ρ is the density of the string, L is the length of n standing wave nodes, the magnitude of the tension on the string is converted into the length of the standing wave nodes, and the length of the standing wave nodes is determined by the position of the standing wave nodes; In the experiment, the coordinate of the tangent position between the fixed pulley and the string on the standing wave experimental bench is x 0 , select the nth node at a distance of x 0 as the research object, and record the positions of this node before and after the liquid film is broken as x 1 and x 2 . The inner diameter and outer diameter of the hanging ring are D 1 and D 2 , and the surface tension coefficient can be obtained as 2. The measuring device for the surface tension coefficient of a liquid based on standing wave vibration according to claim 1, It is characterized in that, A standard meter scale should be installed on the support platform. The string and the ring are connected through a fixed pulley, and the horizontal and stability of the ring should be ensured. The screw lift should be kept stable.

3. The measuring device for the surface tension coefficient of a liquid based on standing wave vibration according to claim 1 or 2, It is characterized in that, A weight pan is installed above the ring to achieve the purpose of stabilizing the ring by adding or reducing weights.

4. The measuring device for the surface tension coefficient of a liquid based on standing wave vibration according to claim 1, It is characterized in that, The diameter, wall thickness, and surface roughness parameters of the ring can be changed, so that the mutual relationship between these parameters of the ring and the surface tension coefficient of the liquid can be studied, which is used for the teaching of physical experiments or other research experiments.

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