Question

The unit of surface tension in SI system is

• A. Dyne/cm²
• B. Newton/m
• C. Dyne/cm
• D. Newton/m²

Answer 1

The correct option is B

Newton/m

Explanation for the correct answer:-

In the case of option B,

1. The surface tension is defined as the force per unit length in the plane of the liquid surface, acting at right angles on either side of an imaginary line drawn on that surface.
2. The SI unit of force is the newton$(N)$, and the SI unit of length is the meter$(m)$.
3. Therefore, the SI unit of surface tension of a body is given as,
   surface tension=$\frac{Force}{Length}=Newton/metre$

Explanation for the incorrect answer:-

In the case of option A,

1. Dyne/cm² is the CGS unit of pressure.
2. Dyne refers to the force required to accelerate the mass of 1g to the rate of 1 cm per second.
3. It is expressed as 1 dyne per square centimeter.
4. Hence, A is incorrect.

In the case of option C,

1. Dyne/cm is the CGS unit of surface tension
2. Hence, option C is incorrect.

In the case of option D,

1. Newton/m² is the SI unit of pressure.
2. One pascal pressure is equal to one newton per square meter.
3. Thus, option D is incorrect.

Hence, option B is the correct answer.