Question

Time period of a block when suspended from the upper plate of a parallel plate capacitor by a spring of stiffness k is T. When block is uncharged. If a charge q is given to the block them, the new time period of oscillation will be

• A. T
• B. > T
• C. < T
• D. T

Answer 1

The correct option is A T

The forces that act on the block are qE and mg. Since qE & mg are constant forces, the only variable elastic force changes by kx. Where x is the elongation in the spring
$\Rightarrow Unbalanced\left(restoring\right)force=F=-kx\Rightarrow -m{\omega }^{2}x=-kx\Rightarrow \omega =\sqrt{\frac{k}{M}}=T$