Vector calculus property: The gradient of any scalar field always yields which type of vector field?
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AA solenoidal field (divergence-free)
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BA conservative field
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CAn irrotational field
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DNone of these
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EBoth conservative and irrotational
Answer
Correct Answer: A conservative field
Explanation
Introduction / Context:In vector calculus, the gradient operator (∇) applied to a scalar field produces a vector field. Recognizing the properties of this gradient field is crucial in electromagnetics, fluid mechanics, and physics.
Given Data / Assumptions:
- We start with a scalar field φ(x, y, z).
- Gradient definition: ∇φ = (∂φ/∂x) i + (∂φ/∂y) j + (∂φ/∂z) k.
- No additional constraints on φ.
Concept / Approach:
The gradient of a scalar field defines a conservative field. By definition, conservative vector fields can be written as the gradient of a scalar potential. A conservative field is also irrotational because curl(∇φ) = 0 always holds (identity of vector calculus).
Step-by-Step Solution:
Given φ(x, y, z), compute ∇φ.Check divergence: may or may not be zero, so it is not necessarily solenoidal.Check curl: ∇ × ∇φ = 0 always, hence irrotational.By definition, any vector field that is the gradient of a scalar potential is called conservative.Verification / Alternative check:
In electrostatics, the electric field E = −∇V is both conservative and irrotational, derived from scalar potential V. This confirms the gradient field's nature.
Why Other Options Are Wrong:
- Solenoidal field: requires ∇·F = 0, which is not guaranteed by a gradient field.
- Irrotational is true, but the canonical name is conservative.
- None: incorrect because gradient always defines a conservative field.
Common Pitfalls:
- Confusing solenoidal (divergence-free) with conservative (gradient of a scalar).
- Overlooking that while gradients are always irrotational, they are defined as conservative fields.
Final Answer:
A conservative field