Question

A constant voltage is applied between the two ends of a uniform metallic wire, heat ‘H’ is developed in it. If another wire of the same material, double the radius and twice the length as compared to the original wire is used then the heat developed in it will be -

Options

• H/2

• H

• 2H

• 4H

Answer 1

2H

Explanation:

`"H" = "V"^2/"R" "t"  &  "H'" = "V"^2/"R"^1 "t"`     `because "V = constant"`

`"H'"/"H" = "V"^2/"R'" "R"/"V"^2 "t"/"t"`

`= "R"/"R'" = rho 1/(pi"r"^2) (2 pi"r"^2)/(rho1)`

`"H'"/"H" = 2/1`

H' = 2H