Electric fields- the force exerted on a given charge

[leah3000]

why is there a different equation for force in a uniformed electric field F=E/Q as opposed to the electric field between a pair of oppositely charged plates F=EQ ?

I thought it would be the same as the field between a pair of oppositely charged plates are also relatively uniformed, in the centre that is.

also how is the equation F=E/Q when E=F/Q ?

 

[Born2bwire]

F=qE, in the absence of a magnetic field, as given by the Lorentz force equation.

 

[SystemTheory]

F = qE is a general relation. In a parallel plate capacitor E is relatively uniform due to the geometry of charge distribution, so F is uniform.

In a more general situation one must examine how the E field varies in space due to charge distribution in the local region, there E varies in space and F varies too. See Coulomb's Law or a reference on electrostatic fields.