Electricity and Magnetism · Problem 10.22

MAGNETIC FIELDS IN MATTER — Edward Purcell & David Morin

Physics — E&M · fringing-field-dipole-approximation

Problem

A parallel-plate capacitor, with a measured capacitance C=250C = 250 picofarads (250⋅10−12250 \cdot 10^{-12} F), is charged to a potential difference of 2000 volts. The plates are 1.5 cm apart. We are interested in the field outside the capacitor, the ``fringing'' field which we usually ignore. In particular, we would like to know the field at a distance from the capacitor large compared with the size of the capacitor itself. This can be found by treating the charge distribution on the capacitor as a dipole. Estimate the electric field strength (a) at a point 3 meters from the capacitor in the plane of the plates; (b) at a point the same distance away, in a direction perpendicular to the plates.

Related theory

Browse the problem library