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Surface tension T of a liquid is best defined as:
AForce per unit length on the surface
BForce per unit area in the bulk
CEnergy per unit volume of liquid
DPressure inside a spherical drop
Answer & Solution
Correct answer: A. Force per unit length on the surface
1. Surface tension T is force per unit length: the force any portion of the surface exerts on an adjacent portion across a line on the surface.
2. SI unit: N m⁻¹. Numerically equal to surface energy per unit area (J m⁻²).
3. Pressure has different dimensions, so (B) and (D) are wrong.
_Source: NCERT Class 11 Physics Ch 9 §9.8 Surface Tension_
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