Question

A fuse wire with a circular cross sectional radius of 0.02 mm flows with a current of 5 amp. For what current, another fuse wire made from the same material with cross-sectional radius of 0.04 mm will flow –

• A. 1.5 amp
• B. 3 amp
• C. 5 amp
• D. None of these

Answer 1

Answer: (D)

None of these

Answer 2

I_max = 5 = $\frac{VA_{1}}{\rho L}$

I'_max = $\frac{VA_{2}}{\rho L}$

$\frac{5}{I'_{\max}}$ = $\frac{A_{1}}{A_{2}} = \left( \frac{0.02}{10.04} \right)^{2}$

I'_max = 20 amp