Show that the force on each plate of a parallel plate capacitor has a magnitude equal to `(1/2)QE`, where Q is the charge on the capacitor, and E is the magnitude of electric field between the plates. Explain the origin of the factor `1/2`.

Explanation

Force `=1/2"QE Work done"=1/2V xx Q`
`F xx d =1/2 xx E.d xx Q" "F=1/2 QE`
The physical origin of the factor `1/2` in the force formula lies in the fact that just outside the conductor, field is E and insde it is zero. So, the average value `E/2` contributes to the force.