Surface Energy of Oil Drop – Rankers Physics

Surface Tension and Viscosity: Practice Problem & Solution

Assertion (A): Surface energy of an oil drop is same whether placed on glass or water surface. Reason (R): Surface energy is dependent only on the properties of oil.  
(1) Both (A) & (R) are true and the (R) is the correct explanation of the (A)
(2) Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
(3) (A) is true but (R) is false
(4) Both (A) and (R) are false

Short Solution (Best for NEET):

To solve this problem, we apply the core principles of Surface Tension and Viscosity. Understanding the underlying formula is key to arriving at the correct answer below:

Concept: Interfacial surface energy. Surface energy (or surface tension) is a property of the interface between two phases. It depends on the intermolecular forces between the molecules of *both* substances forming the interface. Therefore, an oil-glass interface will have different surface energy than an oil-water interface. Both Assertion and Reason are false.

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