A constant voltage is applied between the two ends of a uniform metallic wire. Some heat is developed in it. The heat developed is doubled if

Options

A. both the lengths and radius of the wire are halved
B. both the length and radius of the wire are doubled
C. the radius of the wire is doubled
D. the length of the wire is doubled

Answer

B

Explanation

Heat developed is
`H = (V^(2))/( R ) t`
Heat developed will be doubled when `R` is halved. Further, `R = rho l//( pi r^(2)) and H = V^(2) pi r^(2) t // rho l`. So heat produced when both the length and radius of the wire are doubled.