IntermediateTopic 46 of 104Engineering Mathematics

Divergence and curl

Measure how a vector field spreads out and rotates; appear in fluid and electromagnetic equations.

In depth

Divergence ∇·F measures net outflow per unit volume (sources and sinks); curl ∇×F measures rotation. An incompressible fluid has zero divergence; an irrotational flow has zero curl. Maxwell's equations are written with them.

Key points

  • Divergence is a scalar
  • Curl is a vector
  • ∇×(∇f)=0 and ∇·(∇×F)=0
Example

F=(x,y,0) has divergence 2 and zero curl.

Why it matters

These operators describe how fields expand, rotate and source flows, and they appear directly in the equations of fluids and electromagnetism.

Where this is used

  • Checking whether a velocity field is incompressible using divergence.
  • Computing the vorticity of a rotating flow with curl.
  • Interpreting Maxwell's equations for a charged sphere.

Frequently asked questions

What is Divergence and curl?

Measure how a vector field spreads out and rotates; appear in fluid and electromagnetic equations.

Why is it important to understand divergence and curl?

These operators describe how fields expand, rotate and source flows, and they appear directly in the equations of fluids and electromagnetism.

What does divergence tell me physically?

It measures net outflow from a point. A positive value means the field is spreading out, like a source, and a negative value means it is converging, like a sink.

When is a field curl-free?

When its curl is zero everywhere, the field is irrotational and, in simply connected regions, can be written as the gradient of a potential.

How is Divergence and curl used in practice?

Typical applications include checking whether a velocity field is incompressible using divergence, computing the vorticity of a rotating flow with curl and interpreting Maxwell's equations for a charged sphere.

What should I learn before Divergence and curl?

Study "Line and surface integrals" first (topic 45 of 104 in Engineering Mathematics). It covers the groundwork this topic builds on.

What are the key points of Divergence and curl?

Divergence is a scalar. Curl is a vector. ∇×(∇f)=0 and ∇·(∇×F)=0.

Can you give an example of Divergence and curl?

F=(x,y,0) has divergence 2 and zero curl.

What comes after Divergence and curl?

The next topic is "Green, Stokes and divergence theorems", which builds directly on this one.

How difficult is Divergence and curl?

It is classed as Intermediate in Engineering Mathematics (topic 46 of 104). It is an intermediate topic. Work through the beginner topics in Engineering Mathematics first.

Learning path

Want to practise? Open the interactive course for quick checks, quizzes, simulations and progress tracking.

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