Question

A dielectric slab of thickness d is inserted in a parallel plate capacitor whose negative plate is at $x=0$ and positive plate is at $x=3d$. The slab is equidistant from the plates. The capacitor is given some charge. As one goes from $0$ to $3d$,

• A. the magnitude of the electric field remains the same
• B. the direction of the electric field remains the same
• C. the electric potential increases continuously
• D. the electric potential increases at first, then decreases and again increases.

Answer 1

Answer: (B)

The magnitude and direction of electric field at different points are shown in figure. The direction of the electric field remains the same.
Hence, option $(b)$ is correct. Similarly, electric lines always flow from higher to lower potential, therefore, electric potential increases continuously as we move from $x=0$ to $x=3d$.
Therefore, option $(c)$ is also correct.
The variation of electric field $(E)$ and potential $(V)$ with. $r$ will be as follows
$OA||BC$ and ${\text{(Slope)}}_{OA}>{\text{(Slope)}}_{AB}$
Because $E_{O-d}=E_{2d-3d}$
and $E_{O-d}>E_{d-2d}$