The following dielectric media are used one at a time in between the plates of a parallel plate capacitor. Arrange the capacitances, thus obtained, in the decreasing order of their values.
A. Air
B. Crown glass
C. Diamond
D. Ceramic
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → D, C, B, A
Note: The given answer is as per the official NTA Answer Key. However, none of the given options appears to be strictly correct, because the dielectric constant of crown glass is usually larger than that of diamond, as explained below.
Filling the gap with a dielectric multiplies the capacitance by the dielectric constant K, so the capacitances are in the same order as the dielectric constants.
\( C = KC_0 \)
Typical dielectric constants:
\( \text{Air (A): } K \approx 1.0006 \)
\( \text{Diamond (C): } K \approx 5.7 \)
\( \text{Crown glass (B): } K \approx 6 \text{ to } 8 \text{ (depending on its composition)} \)
\( \text{Ceramic (D): hundreds to thousands for the ceramics used in capacitors} \)
Ceramic has by far the largest dielectric constant and air the smallest, so D comes first and A last. Option (3) is the only option with this order.
Strictly, crown glass (B) should come before diamond (C), giving the order D, B, C, A, which is not among the options; the answer given by NTA assumes that diamond has the larger dielectric constant.