Between the plates of a parallel plate capacitor a dielectric plate in introduced just to fill the complete space between the plates. The capacitor is charged and later disconnected from the battery. The dielectric plate is then slowly drawn out of the capacitor plates. the plot of the potential difference across the plates and the length of the dielectric plate drawn out is

Options

A. Figure 4
B. figure 3
C. figure 2
D. figure 1

Answer

C

Explanation

When the charged capacitor is disconnected from the battery the cahrge remains constant
and `because C=(Q)/(V)" "therefore C prop(1)/(V) or Vprop(1)/(C)`
When the dielectric completely fills the space between the plates, its capacity `C=(KA epsi_(0))/(d)` is maximum. when it is slowly withdrawn, the capacity gradually decreases and when it is fully withdrawn, K=q for air. As C is decreased, P.D. across the plates (V) is increased and then it becomes constant. this is shown in fiigure (2).