| Directions: In the following questions, a statement of Assertion (A) is followed by a statement of Reason (R). Mark the correct choice as: |
| Assertion (A): The dielectric constant for metals is infinity. |
| Reason (R): When a charged capacitor is filled completely with a metallic slab, its capacity becomes very large. |
A) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A)
B) Both Assertion (A) and Reason (R) are true but Reason (R) is not the correct explanation of Assertion (A)
C) Assertion (A) is true but Reason (R) is false
D) Assertion (A) is false and Reason (R) is also false
Correct Answer: C
Solution :
(c) The capacitance of a capacitor filled partially with a dielectric of thickness t given by \[C=\frac{{{\varepsilon }_{0}}A}{d-t\left( 1-1/K \right)}\] For metals, \[K=\infty \] \[\therefore \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,C=\frac{{{\varepsilon }_{0}}A}{d-t}\] Now, if the capacitor is filled completely with a metallic slab, then t = (d) \[\therefore \,\,C=\infty \]i.e., when a charged capacitor filled fully with a metallic slab, then capacitor is short circuited i.e., it will no more work as a capacitor.
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