Question

The electric field between the plates of a parallel plate capacitor when connected to a certain battery is $154\text{N/C}$. If the space is filled completely with a material of dielectric constant $2$ without removing the battery, the field will become equal to

• A. $154\text{N/C}$
• B. $308\text{N/C}$
• C. $77\text{N/C}$
• D. $\text{Data insufficient}$

Answer 1

The correct option is A $154\text{N/C}$

As the battery remains connected, the potential difference across the capacitor will remain unchanged and equal to that of the battery.

From the equation, $V=Ed$, we see that the electric field between the plates also remains unchanged as $V$ and $d$ both are unchanged.

The polarization of the dielectric tries to reduce the electric field in the space between the plates but this is prevented by the increase of charge on the plates delivered by the battery to hold the potential difference $V$ constant.

Hence, option $\left(a\right)$ is correct.

Key concept- Electric field between the plates of a capacitor with dielectric remains unchanged if the battery remains connected.