Figures show four pairs of parallel plates P, Q, R and S with the same separation and the electric potential of each plate. The electric field between the plates is uniform and perpendicular to the plates. Arrange the plates in descending order of the magnitude of the electric field between the plates.
(A) P
(B) Q
(C) R
(D) S
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → (B), (C), (A), (D)
For a uniform field between parallel plates, \( E = |\Delta V|/d \). All four pairs have the same separation d, so the field is proportional to the potential difference between the plates; the individual potentials do not matter.
\( \text{P: } |100 - (-50)| = 150\,\mathrm{V} \)
\( \text{Q: } |200 - (-20)| = 220\,\mathrm{V} \)
\( \text{R: } |(-400) - (-200)| = 200\,\mathrm{V} \)
\( \text{S: } |160 - 40| = 120\,\mathrm{V} \)
Descending order of field: Q (220 V), R (200 V), P (150 V), S (120 V), i.e. (B), (C), (A), (D).