The same mass of copper is drawn into two wires `1mm` and `2mm` thick. These two wires are connected in series to the source of current .What is the ratio of the heat produced in the wires ?

Answer

`16 : 1`

Explanation

`H = l^(2)R = l^(2)(rho l)/(pi r^(2)) (m = pir^(2)l d)`
`= l^(2) -(rho xx m)/((pi r^(2) l xx pi r^(2) d) = (l^(2)rho m)/(pi^(2) r^(2) d)`
So ` H = (1)/(r^(4)) :. (R_(1))/(R_(2)) = ((r_(1))/(r_(2)))^(4) = ((2)/(1))^(2) = 16 : 1`