Del Operator for Cylindrical Coordinate

In summary: In summary, the del operator for cylindrical coordinates is the upper one because the unit vectors change with position in this system. The 1/r term arises from the fact that the rate of increase per distance in the eθ direction is r times the rate of increase per angle. This can be derived using general curvilinear coordinates or through a specific derivation in "Engineering Electromagnetics" by Nathan Ida, available for preview on Google Books.
  • #1
Harmony
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Why is the del operator for cylindrical coordinate the upper one and not the lower one? How does the 1/r term arises?
 
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  • #2
You could read about general curvilinear coordinates and that should answer your question (plus it will also explain the factors in other expressions from different coordinate systems like e.g. spherical polar coordinates). Basically the unit vectors change with position in cylindrical coordinates and that is why the factor appears.

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  • #3
Hi Harmony! :smile:

(have a del: ∇ and a theta: θ and a curly d: ∂ :wink:)
Harmony said:
Why is the del operator for cylindrical coordinate the upper one and not the lower one? How does the 1/r term arises?

().eθ has to be the rate of increase per distance in the eθ direction …

but ∂/∂θ is the rate of increase per angle

and distance (in the eθ direction) is r times angle. :wink:
 
  • #4
  • #5
Also, in case the link I provided in my previous post becomes unavailable, PF members arildno and HallsOfIvy walk through the same derivation in another thread here on Physics Forum.

Check it out under Physics Forums>Mathematics>General Math -> Thread = "Del operator with coordinate transformations"
 

What is the del operator in cylindrical coordinates?

The del operator, denoted as ∇, is a vector differential operator used in cylindrical coordinates to represent the gradient, divergence, and curl of a scalar or vector field. It is defined as ∇ = 1/ρ ∂/∂ρ + 1/ρ ∂/∂θ + ∂/∂z.

What is the gradient in cylindrical coordinates?

The gradient is a vector quantity that represents the rate of change of a scalar field in a given direction. In cylindrical coordinates, the gradient is given by ∇φ = ∂φ/∂ρ ρ̂ + 1/ρ ∂φ/∂θ θ̂ + ∂φ/∂z ẑ.

What is the divergence in cylindrical coordinates?

The divergence is a scalar quantity that represents the flow of a vector field out of a given point. In cylindrical coordinates, the divergence is given by ∇·F = 1/ρ (∂(ρFρ)/∂ρ + ∂Fθ/∂θ) + ∂Fz/∂z.

What is the curl in cylindrical coordinates?

The curl is a vector quantity that represents the circulation of a vector field around a given point. In cylindrical coordinates, the curl is given by ∇×F = 1/ρ (∂Fz/∂θ − ∂Fθ/∂z) ρ̂ + (1/ρ ∂(ρFρ)/∂z − ∂Fz/∂ρ) θ̂ + (1/ρ ∂Fθ/∂ρ − ∂(ρFρ)/∂θ) ẑ.

What are some common applications of the del operator in cylindrical coordinates?

The del operator in cylindrical coordinates is commonly used in fields such as electromagnetism, fluid dynamics, and heat transfer. It is used to solve partial differential equations and to analyze the behavior of vector fields in cylindrical systems.

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