Physics

Problem

A horizontal upper plate of a capacitor is suspended by a spring of spring constant

k = 100\,\text{N/m}

. The lower plate is fixed. The area of the plates is

A = 0.01\,\text{m}^{2}

. When the capacitor is uncharged, the separation is

d = 5\,\text{mm}

. A voltage

V

is applied, causing the upper plate to move down by

1\,\text{mm}

in equilibrium. Calculate the value of

V

. (Take

\varepsilon_{0} = 8.85 \times 10^{-12}\,\text{F/m}