Question

When a dielectric material is introduced between the plates of a charged condenser, after disconnected the battery the electric field between the plates:
(A) Decreases
(B) Increases
(C) Does not change
(D) May increase or decrease

Answer 1

Hint: It is given that a charged condenser is connected to a battery which is supplying current to the plates. When a di-electric is introduced, the electric field between the plates becomes inversely proportional to the di-electric constant. Using these, justify your answer.

Complete Step by step solution:
 When a battery is connected to a charge conducting plate, there will flow of charge and hence there will be an electric field E flowing between the plates. The electric field is mathematically represented as the ratio of voltage flowing between the plates and the distance between the plates.
$$\Rightarrow E={\displaystyle \frac{V}{d}}$$
Now, when a dielectric material of dielectric constant k is introduced , the electric field directly varies upon the di-electric constant introduced. When the battery is disconnected, the voltage will remain constant in the conducting plate and won’t change. However, there will be a significant change in the flow of charge from one plate to another separated by a distance.
Due to the presence of a di-electric material between the conducting plates the flow of charge will be directly proportional to the Voltage and since the voltage becomes constant after the disconnection of the battery, there will be a difference in change. The presence of dielectric will reduce the electric field flow.

Hence , option (a) is the right answer for the given question.

Note: In a parallel plate capacitor setup, the capacitance depends upon the charge flowing between the plate and the Voltage applied through the circuit, the area between the plate and the permissibility factor.