Q: In the given figure the capacitor of plate area A is charged upto charge q. The ratio of elongations (neglect force of gravity) in springs C and D at equilibrium position is

(a) $ \displaystyle \frac{k_1}{k_2} $

(b) $ \displaystyle \frac{k_2}{k_1} $

(c) $ \displaystyle k_1 k_2 $

(d) $ \displaystyle \sqrt{ \frac{k_1}{k_2}} $

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Ans: (b)

Sol: Force acting between plates of capacitor is attractive & it is

$ \displaystyle F = \frac{q^2}{2 \epsilon_0 A} $

$\displaystyle k_1 x_1 = k_2 x_2 $

$\displaystyle \frac{x_1}{x_2} = \frac{k_2}{k_1} $