JEE MainPhysicsCapacitance
A parallel plate capacitor has a plate separation d . When a metal sheet of thickness t is introduced parallel to the plates, the capacitance of the system increases by 25 % . The thickness t of the metal sheet is:
Options
- Ad 4
- B4d 5
- Cd 5
- D5d 4
Correct answer
C. d 5
Step-by-step solution
The initial capacitance of the parallel plate capacitor is C = ₀ A d . When a metal sheet of thickness t is inserted, the new capacitance is C' = ₀ A d - t . It is given that the capacitance increases by 25 % , so the new capacitance is: C' = C + 0.25C = 1.25C = 5 4 C Substituting the expressions for C and C' : ₀ A d - t = 5 4 ( ₀ A d ) 1 d - t = 5 4d 5(d - t) = 4d 5d - 5t = 4d 5t = d t = d 5 Answer: d 5