An infinite thread of charge density λ lies along z-axis. The potential difference between points A(4, 3, 4) and B(3, 4, 0) is
Equipotential surfaces are coaxial cylinders, therefore (4, 3, 4) and (3, 4, 0) lie on equipotential surface.
An arc of radius r carries charge. The linear density of charge is λ and the arc subtends an angle π3 at the centre. What is electric potential at the centre?