Which of the following is a dimensional constant?

A dimensional constant is a physical constant that has units (dimensions) associated with it.

Explanation:

• Physical constants are of two types:
1. Dimensional constants – have units
2. Dimensionless constants – have no units

Examples of Dimensional Constants:

• Gravitational constant (G) → unit: N·m²/kg²
• Planck’s constant (h) → unit: J·s
• Speed of light (c) → unit: m/s

Examples of Dimensionless Constants:

• Coefficient of friction
• Refractive index
• Poisson’s ratio

Key Insight:

• If a constant has units, it is dimensional
• If it is just a number without units, it is dimensionless

Conclusion:

Constants like G, h, and c are dimensional constants because they possess physical units.