A thin copper wire of length `l` metre increases in length by `2%` when heated through `10^(@)C`. What is the percentage increase in area when a square copper sheet of length `l` metre is heated through `10^(@)C`

Answer

`1/(4pi in_(0))(qQ)/(d(d+L))`

Explanation

We consider an element of thickness dx at a distance x from q

Force on `q=int1/(4pi in_(0))xx(dQ.q)/x^(2)`
Where `dQ=Q/L dx` then, `F=(KQq)/(L) underset(d)overset(d+L)(int)(dx)/x^(2)=(KQq)/(d(d+L))`