PHYSICS · Multi-part · CBSE · Physics · Electrostatic Potential and Capacitance · Electrostatic Potential and Capacitance
Problem
Parallel conducting plates of area 200cm2 are 8.0mm apart. A dielectric slab of thickness 3.0mm and relative permittivity κr=4.0 completely fills the space adjacent to the positive plate, leaving the remaining 5.0mm as air. Assume surface charge density on the plates is uniform and fringe effects are negligible.
(a) Draw a neat, labelled sketch showing the arrangement of the plates, dielectric slab, and air gap.
(b) Obtain expressions for the magnitude of the electric field in (i) the dielectric region and (ii) the air region in terms of the free surface charge density σ and fundamental constants.
(c) Hence derive an expression for the potential difference between the plates.
(d) If the electric field in the air gap is measured to be 1.2×105V m−1, calculate the potential difference between the plates.