(1) Calculate the field strength distribution first, and then calculate the potential;

② Using the principle of potential superposition, the potential can be directly calculated.

Here, the calculation is based on the principle of potential superposition.

Uo = ∫ dU

= ∫ dq / (4π ε0 r)

= ∫(R 1，R2) σ 2π r dr / (4π ε0 r)

= σ (R2 - R 1) / (2 ε0)