Q7 of 94 Page 164

When a dielectric slab is gradually inserted between the plates of an isolated parallel-plate capacitor, the energy of the system decreases. What can you conclude about the force on the slab exerted by the electric field?


When a dielectric slab is gradually inserted between the plates of an isolated parallel-plate capacitor, the energy of the system come out to be a linear function of xdisplacement of the slab inside capacitor measured from the center of the plate).


since x decreases, the energy of the system decreases.


We know that



Where


is the rate of change of potential energy function with x


-ve sign indicates that force is in negative direction when energy increases with respect to x)


Therefore, Force on the slab exerted by the electric field is constant and positive.


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