When a current is passed in a conductor, a 3oC rise in temperature is observed. If the strength of current is made thrice, then rise in temperature will approximately be:

Amount of heat produced in a certain amount of time by passing a current I through the wire, H ∝ I². This heat, H, is used to rise the temperature of the wire. Thus heat added, H ∝ ΔT. So, I² ∝ ΔT. Thus as current becomes thrice, the change in temperature becomes 9 times its initial value. Thus new change in temperature = 9 × 3 ℃ = 27 ℃