NEET Physics: excess of pressure across a curved surface Practice Questions

Correct answer: B — ΔP = γ/ R

For a single curved interface, the excess pressure difference is fundamentally related to the surface tension (γ) and the radius of curvature (R) via the Laplace pressure equation (ΔP = γ/R).

Correct answer: D — ΔP = 2γ/R

The excess pressure is mathematically defined by the Laplace equation, ΔP = 2γ/R, where γ is surface tension and R is the radius of curvature.

Correct answer: C — Be doubled

Since ΔP ∝ γ, if the surface tension (γ) is doubled and curvature is constant, the excess pressure across the surface will also double.

Correct answer: A — It is halved

Since ΔP = 2γ/R, if R is doubled and γ is constant, the pressure ΔP is halved.

Correct answer: A — the cohesive forces between the liquid molecules

The excess pressure across a curved surface (surface tension) arises because the liquid molecules at the surface are only attracted inward by neighboring molecules (cohesive forces), resulting in a net inward force, which manifests as an excess pressure if considered in terms of forces per unit area.

Correct answer: B — Surface tension

Surface tension (γ) is defined as the force acting per unit length along the boundary of the liquid surface. This represents the excess energy stored at the surface.

Correct answer: A — the surface tension and the length of the line of contact

The excess pressure across a curved surface is a manifestation of the surface tension (γ). The pressure difference (ΔP) is defined by the relationship ΔP = γ· L, where L is the length of the line of contact.

Correct answer: B — It is a measure of the work done to increase the surface area.

Surface tension is the energy required to increase the surface area of the liquid by a unit amount, representing the cohesive forces acting along the surface.

Correct answer: C — Surface Tension

The excess pressure existing across the curved surface of a liquid is defined by the property known as surface tension. Surface tension arises due to the cohesive forces acting along the surface, resulting in a net inward force per unit length, which manifests as excess pressure.

Correct answer: A — The surface area and surface tension.

The total force due to surface tension is the product of the surface tension (γ) and the total length of the line (which is proportional to the surface area).

Correct answer: A — Surface forces

The forces acting at the interface between two immiscible liquids are due to the cohesive forces (surface tension) acting along the boundary, which creates an excess pressure difference.

Correct answer: D — J/m

Surface tension is a force per unit length, and its SI unit is Newton per meter (N/m). However, in contexts where pressure difference is involved, the energy density is often related to J/m², but surface tension itself is measured in force/length (N/m). The term often used conceptually in relation to surface energy density is J/m², but for the force itself, N/m is correct. Given standard physics definitions, N/m is the fundamental unit, but if we consider the energy density, J/m² is also relevant. For simplicity in this context, N/m is the direct force measure.

Correct answer: C — The radius of curvature

The excess pressure (P₍excess)) is related to the surface tension (γ) and the principal radii of curvature (R) by the Laplace equation. For a simple surface, the pressure difference is inversely related to the radii of curvature.

Correct answer: C — Surface energy

The excess pressure across a curved surface arises from the cohesive forces acting along the line of contact, which manifest as surface tension. Surface tension is a measure of the energy stored in the surface, which is directly related to the excess pressure.

Correct answer: D — It causes the liquid to minimize its total surface area.

Liquids naturally tend to minimize their surface energy. Because surface energy is proportional to the surface area, the liquid adopts shapes that minimize the surface area for a given volume, resulting in curved interfaces.