Define Bulk modulus of elasticity and write an expression in terms of pressure .P., volume .V. and change in volume `.DeltaV.`.

Explanation

### Step-by-Step Solution

1. **Definition of Bulk Modulus of Elasticity**:
The bulk modulus of elasticity (B) is defined as the ratio of normal stress to the volume strain. It quantifies how incompressible a material is when subjected to uniform pressure.

2. **Understanding Normal Stress**:
Normal stress (σ) is defined as the force (F) applied per unit area (A). Mathematically, it can be expressed as:
\[
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