A parallel-plate capacitor of area \(A\), plate separation \(d\) and capacitance \(C\) is filled with four dielectric materials having dielectric constants \(k_1, k_2,k_3\) and \(k_4\) as shown in the figure below. If a single dielectric material is to be used to have the same capacitance \(C\) in this capacitor, then its dielectric constant \(k\) is given by:
1. | \( {k}={k}_1+{k}_2+{k}_3+3 {k}_4\) |
2. | \({k}=\frac{2}{3}\left({k}_1+{k}_2+{k}_3\right)+2 {k}_4\) |
3. | \({k}=\frac{2}{3} {k}_4\left(\frac{{k}_1}{{k}_1+{K}_4}+\frac{{k}_2}{{k}_2+{k}_4}+\frac{{k}_3}{{k}_3+{k}_4}\right)\) |
4. | \(\frac{1}{{k}}=\frac{1}{{k}_1}+\frac{1}{{k}_2}+\frac{1}{{k}_3}+\frac{3}{2 {k}_4}\) |
1. | \(1:2\) | 2. | \(2:3\) |
3. | \(3:2\) | 4. | \(2:1\) |
Assertion (A): | In the absence of an externally applied electric field, the displacement per unit volume of a polar dielectric material is always zero. |
Reason (R): | In polar dielectrics, each molecule has a permanent dipole moment, but these dipoles are randomly oriented when there is no external electric field. |
1. | Both (A) and (R) are True and (R) is the correct explanation of (A). |
2. | Both (A) and (R) are True but (R) is not the correct explanation of (A). |
3. | (A) is True but (R) is False. |
4. | Both (A) and (R) are False. |