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Q43ModerateVector Calculus

Consider the following statements regarding vector calculus:
1. The divergence of a vector field represents the net outward flux per unit volume from a point and indicates the presence of sources or sinks.
2. The curl of a vector field measures the rotational tendency of the field and is zero for conservative fields.
3. The gradient of a scalar field always results in a scalar quantity representing rate of change.
4. Divergence theorem relates surface integral of a vector field over a closed surface to volume integral of divergence.
Which of the above statements is/are correct?

Answer & step-by-step solution
Correct answer: A. 1, 2 and 4 only
Quick explanation

The three basic vector differential operators have distinct outputs: gradient maps scalar→vector, divergence maps vector→scalar, and curl maps vector→vector. Remembering input/output type is often enough to eliminate distractors. Key relation: grad φ=∇φ; div A=∇·A; curl A=∇×A; ∮_S A·dS = ∫_V (∇·A)dV.

Exam focus: Use the mnemonic: Grad grows a scalar into a vector; Div gives a scalar; Curl gives a vector. Common trap: Calling gradient a scalar because the original field is scalar.

grad φ=∇φ; div A=∇·A; curl A=∇×A; ∮_S A·dS = ∫_V (∇·A)dV.

Statement-wise Verification

  • Statement 1 - Correct.
    The divergence of a vector field represents the net outward flux per unit volume from a point and indicates the presence of sources or sinks.
    Divergence is a scalar measuring net outward flux density/source strength at a point.
  • Statement 2 - Correct.
    The curl of a vector field measures the rotational tendency of the field and is zero for conservative fields.
    Curl is a vector measuring local rotational tendency; for a sufficiently smooth conservative field F=−∇V, ∇×F=0.
  • Statement 3 - Incorrect.
    The gradient of a scalar field always results in a scalar quantity representing rate of change.
    ∇φ is a vector field pointing in the direction of steepest increase of scalar φ.
  • Statement 4 - Correct.
    Divergence theorem relates surface integral of a vector field over a closed surface to volume integral of divergence.
    The divergence theorem converts closed-surface flux into a volume integral of divergence.

Core Concept

The three basic vector differential operators have distinct outputs: gradient maps scalar→vector, divergence maps vector→scalar, and curl maps vector→vector. Remembering input/output type is often enough to eliminate distractors.

Formula / Key Relationship

grad φ=∇φ; div A=∇·A; curl A=∇×A; ∮_S A·dS = ∫_V (∇·A)dV.

Step-by-Step Check

Type-checking immediately disproves statement 3. The geometric meanings and divergence theorem confirm 1, 2 and 4, yielding A.

Why the Other Options Are Wrong

Option B is incorrect because it includes incorrect statement(s) 3 and omits correct statement(s) 2, 4. Option C is incorrect because it includes incorrect statement(s) 3 and omits correct statement(s) 1, 4. Option D is incorrect because it includes incorrect statement(s) 3.

Answer-Key Verification Note

The uploaded provisional key marks C . After independent technical verification, the defensible answer is A . This discrepancy is stated explicitly rather than silently copying the provisional key.

Exam Shortcut / Approach

Use the mnemonic: Grad grows a scalar into a vector; Div gives a scalar; Curl gives a vector.

Common Mistake

Calling gradient a scalar because the original field is scalar.

Quick Revision

Vector Differential Operators is linked with Gradient Divergence and Curl, Vector Calculus and Electromagnetic Fields. Use the mnemonic: Grad grows a scalar into a vector; Div gives a scalar; Curl gives a vector.

Exam tipUse the mnemonic: Grad grows a scalar into a vector; Div gives a scalar; Curl gives a vector.
Verified · SRO editorial desk Report
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