Electrostatic Force in a Capacitor with Dielectric – Rankers Physics

Capacitor With Dielectrics: Practice Problem & Solution

Assertion: The electrostatic force between the plates of a charged isolated capacitor decreases when dielectric fills whole space between plates. Reason: The electric field between the plates of a charged isolated capacitor increases when dielectric fills whole space between plates.
Both Assertion and Reason are true and Reason is the correct explanation of Assertion.
Both Assertion and Reason are true but Reason is not correct explanation of Assertion.
Assertion is true but Reason is false.
Assertion and Reason are false.

Short Solution (Best for NEET):

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

For an isolated capacitor, force is \(F = \frac{Q^2}{2 K A \varepsilon_0}\) which decreases with dielectric (\(K > 1\)). The electric field \(E = \frac{E_0}{K}\) also decreases. Hence, Reason is false.

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