Question

The electric field and capacitance of a capacitor in the absence of dielectric material are $E$ and $C$, respectively. When the capacitor is filled with a dielectric material, the electric field and capacitance become $E'$ and $C'$, respectively. Which of the following is(are) correct?

• A. $E'>E$ and $C' = C$
• B. $E'<E$ and $C'>C$
• C. $E' = E$ and $C'>C$
• D. $E'>E$ and $C'<C$

Hint:

Dielectric → lowers field, increases capacitance.

Answer 1

The Correct Option is B, C

Step 1: Effect of dielectric on electric field.
A dielectric reduces the effective electric field inside the capacitor: $E' = \dfrac{E}{\kappa}$, where $\kappa>1$. Thus, $E'<E$.
Step 2: Effect of dielectric on capacitance.
Capacitance increases by a factor $\kappa$: $C' = \kappa C$ So $C'>C$.
Step 3: Evaluate options.
Only option (B) correctly states both effects: reduced electric field and increased capacitance.
Step 4: Conclusion.
Thus, $E'<E$ and $C'>C$.