Electrostatics 5 Question 16
18. A parallel plate capacitor of capacitance $90 pF$ is connected to a battery of emf $20 V$. If a dielectric material of dielectric constant $K=5 / 3$ is inserted between the plates, the magnitude of the induced charge will be
(2018 Main)
(a) $0.9 \mu C$
(b) $1.2 \mu C$
(c) $0.3 \mu C$
(d) $2.4 \mu C$
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Solution:
$$ \begin{aligned} Q & =K C _0 V \\ \left|Q _{\text {in }}\right| & =\left|Q \quad 1-\frac{1}{K}\right| \\ & =\left(90 \times 10^{-12}\right)(20) \frac{5}{3} \quad 1-\frac{3}{5} C \\ & =1200 \times 10^{-12} C=1.2 \mu C \end{aligned} $$
