The electric potential at the centre of two concentric half rings of radii R1 and R2, having same linear charge density λ is
(2)
dv=14πε0λ dℓR ; v∫dv=14πε0λℓR
Potential at centre, V=V2+V1
⇒V=(λ.πR2)4πε0R2+(λ.πR1)4πε0R1=λ2ε0