Capacitor with Dielectric and Conductor – Rankers Physics

Parallel Plate Capacitor: Practice Problem & Solution

Assertion (A): If capacitor is filled with, same thickness \(t < d\) of dielectric and conducting sheet one after another, then capacitance are \(C_1\) and \(C_2\) respectively then \(C_1 < C_2\). Reason (R): Capacitance is more in presence of metal sheet in compare to dielectric sheet as  
(1) Both (A) & (R) are true and the (R) is the correct explanation of the (A)
(2) Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
(3) (A) is true but (R) is false
(4) Both (A) and (R) are false

Short Solution (Best for NEET):

To solve this problem, we apply the core principles of Parallel Plate Capacitor. Understanding the underlying formula is key to arriving at the correct answer below:

Assertion (A): For a dielectric slab of thickness \(t\) and dielectric constant \(K\), \(C_1 = \frac{\epsilon_0 A}{d-t+t/K}\). For a conducting slab of thickness \(t\), \(C_2 = \frac{\epsilon_0 A}{d-t}\). Since \(K>1\), \(d-t+t/K > d-t\), implying \(C_1 < C_2\). So (A) is true.


Reason (R): A metal (conductor) effectively acts as a dielectric with \(K = \infty\), which makes its capacitance higher than a dielectric with a finite \(K\). So (R) is true and correctly explains (A).

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