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1 Answer. Basically it makes things easier if your coordinates look like the problem. If you have a problem with cylindrical symmetry, like the magnetic field of a wire, use those coordinates. There are many other systems possible.
Beside this, why do we use spherical coordinates?
Spherical coordinates determine the position of a point in three-dimensional space based on the distance ρ from the origin and two angles θ and ϕ. If one is familiar with polar coordinates, then the angle θ isn't too difficult to understand as it is essentially the same as the angle θ from polar coordinates.
People also ask, what is dS in cylindrical coordinates?
To get dS, the infinitesimal element of surface area, we use cylindrical coordinates to parametrize the cylinder: (6) x = a cos θ, y = a sin θ z = z . Its area dS is the product of its height and width: (7) dS = dz · adθ .
Figure 1: A point expressed in cylindrical coordinates. To convert from cylindrical to rectangular coordinates we use the relations x = r cosθ y = r sinθ z = z. To convert from rectangular to cylindrical coordinates we use the relations r = √ x2 + y2 tanθ = y x z = z.