Question

A fuse wire with radius 1 mm blows at 1.5 amp. The radius of the fuse wire of the same material to blow at 3A will be

• A. $4^{1/3}mm$
• B. $3^{1/4}mm$
• C. $2^{1/2}mm$
• D. $3^{1/2}mm$

Answer 1

Answer: (A)

$4^{1/3}mm$

Answer 2

$i \propto r^{3/2} \Rightarrow$ $\frac{r_{2}}{r_{1}} = \left( \frac{i_{2}}{i_{1}} \right)^{3/2} = \left( \frac{3}{1.5} \right)^{2/3} = (4)^{1/3}$

$\Rightarrow r_{2} = (4)^{1/3} \times r_{1} = 4^{1/3}$ ( r₁ = 1 mm)