If two parallel plates A and B separated 4 cm apart have potentials -80V and + 80V respectively. The direction of E is from B to A. Equipotentials are parallel to the plates with a pd of 40 V every one cm. This will mean the electric field strength E is 4000 Vm-1.
A charge q released from the centre of the plates AB means moving 2 cm across to one of the plate will mean work involved = qV where q is the charge moved and V , the p.d = 80 V. Work done by electric field will be the ke of the charge when it hit the plate. Therefore KE = qV.
