The electric field $\mathbf{E}$ and electric potential $V$ are related by the equation $\mathbf{E} = -\frac{dV}{dr}$ (in one dimension) or $\mathbf{E} = -\nabla V$ (gradient of potential) [NCERT Class 12, Physics Part I, Sec 2.6, Eq 2.20].

1. Given: The electric potential $V$ is $5 \text{ V}$ (a constant value) throughout the volume.
2. Concept: The electric field represents the rate of change of potential with respect to distance. Since the potential is constant, it does not change with position.
3. Calculation: The derivative of a constant with respect to position is zero. $E = -\frac{d(5)}{dr} = 0$ Therefore, the electric field in a region of constant potential is always zero. This is analogous to the field inside a charged conductor where the potential is constant and the field is zero [NCERT Class 12, Physics Part I, Sec 2.9].