A parallel-plate capacitor of capacitance 90 pF is connected to a 20 V battery. A dielectric of dielectric constant K = 5/3 is inserted between the plates. Find the magnitude of the induced charge.
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Question

A parallel-plate capacitor of capacitance 90 pF is connected to a 20 V battery. A dielectric of dielectric constant K = 5/3 is inserted between the plates. Find the magnitude of the induced charge.

G1 Physics · Accepted Answer

Initial free charge is Q₀ = CV = (90 pF)(20 V) = 1.8 nC. With the battery connected, the induced/additional charge magnitude is (K−1)Q₀ = (2/3)(1.8 nC) = 1.2 nC. Hence option D.