Understanding the Wilhelmy Plate Method for Calculating Surface Tension

In summary, there are two different formulae for calculating surface tension using the Wilhelmy plate method. One divides the surface tension force by the perimeter of the plate, while the other divides by twice the perimeter. It is unclear which one is correct, but it may be due to the use of one roughened side or both sides of the plate.
  • #1
lyhuyen
I found two different resources which give two different but similar formulae to calculate surface tension for Wilhelmy plate method: in one formula, the surface tension (ST) force is devided by the perimetor of the plate; in the other one, ST force is divided by twice the perimetor.

Which one is correct?

And can someone please explain me why it is the perimetor? Since the liquid doesn't wet the whole rectangular plate, shouldn't it be twice the length of the plate? (given that the thinness is negligible).

Thanx in advance.
 
Physics news on Phys.org
  • #2
It would help if you gave some links but I think I see your problem. In one of the links I read, they roughen up one side of the plate and in another, they use both sides. That could account for your unexplained factor of two??
 

1. What is the Wilhelmy Plate Method for calculating surface tension?

The Wilhelmy Plate Method is a technique used to measure the surface tension of a liquid. It involves suspending a rectangular plate or wire in the liquid and measuring the force required to pull it out of the liquid. This force is then used to calculate the surface tension of the liquid.

2. Why is the Wilhelmy Plate Method used to measure surface tension?

The Wilhelmy Plate Method is commonly used because it is a simple and accurate technique for measuring surface tension. It also allows for the measurement of surface tension for a wide range of liquids, including both polar and non-polar liquids.

3. What are the advantages of using the Wilhelmy Plate Method?

One of the main advantages of the Wilhelmy Plate Method is its high accuracy. It also requires minimal equipment and can be performed relatively quickly. Additionally, this method allows for the measurement of surface tension at various temperatures and can provide information about the surface properties of a liquid.

4. Are there any limitations to the Wilhelmy Plate Method?

While the Wilhelmy Plate Method is a widely used and reliable technique, it does have some limitations. One potential limitation is that the shape and size of the plate or wire used can affect the results of the measurement. Additionally, the presence of impurities or surface-active substances in the liquid can also impact the accuracy of the measurement.

5. How is the surface tension calculated using the Wilhelmy Plate Method?

The surface tension is calculated by dividing the measured force by the wetted perimeter of the plate or wire. The wetted perimeter is the length of the plate or wire that is in contact with the liquid. The resulting value is typically reported in units of N/m (newtons per meter).

Similar threads

  • Introductory Physics Homework Help
Replies
4
Views
758
  • Other Physics Topics
Replies
1
Views
1K
Replies
17
Views
461
  • Other Physics Topics
2
Replies
43
Views
5K
  • Introductory Physics Homework Help
Replies
11
Views
309
Replies
2
Views
714
  • Classical Physics
Replies
23
Views
1K
Replies
11
Views
281
  • Introductory Physics Homework Help
Replies
21
Views
607
  • Introductory Physics Homework Help
Replies
1
Views
877
Back
Top