question_answer

Directions : In the following question more than one of the answers given may be correct. Select the correct answer and mark it according to the code:

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\[x\]goes from 0 to 3d  the magnitude of the electric field remains the same (2) the directions of the electric field remains the same (3) the electric potential increases at first, then decreases and again increases (4) the electric potential increases continuously

A)   1, 2 and 3 are correct

B)  1 and 2 are correct

C)   2 and 4 are correct

D)  1 and 3 are correct

Correct Answer: C

Solution :

                 The magnitude and direction of electric field at different points are shown in figure. The direction of the electric field remains the same. Similarly electric lines always flow from higher to lower potential, therefore, electrical potential increases continuously as we more from\[x=0\]to\[x=3d\]. The variation of electric field (E) and potential (V) with x will be as follow. \[OA|\,|BC\]and\[{{(slope)}_{AB}}>{{(slope)}_{AB}}\] Because               \[{{E}_{0-d}}={{E}_{2d-3d}}\] and                        \[{{E}_{0-d}}>{{E}_{d-2d}}\]