Question

Two fuse wires are made of the same material . The radius of first and second wires are `r_(1) = 2mm` and `r_(2)= 4mm`. The first wire blows when a current of `15A` passes through it. Find the current required to blow the second wire.

Answer 1

For a fuse wire of given material
`i^2 prop r^3`
`(i_2)/(i_1) = ((r_2)/(r_1))^(3//2)`
`(i_2)/(15) = (4/2)^(3/2) = 2sqrt(2)`
`i_(2) = 30sqrt(2)A`.