Question

a copper wire has diameter 0.5 mm and resistivity 1.6 into 10 power minus 8 ohm metre what will be the length of the wire to make the resistance 12 ohm how much will heat is cyst of another copper wire to same length but half the diameter​

Answer 1

Explanation:

Given :

Resistivity ρ = 1.6 × 10⁻⁸ Ω m

Resistance R = 10 Ω

Diameter d = 0.5 mm

= > Radius r = 0.25 mm = 0.25 × 10⁻³ m = 2.5 × 10⁻⁴ m

= > Area A = 6.25 π × 10⁻⁸ m²

We are asked to find length L :

We know :

R = ρ ( L ) / ( A )

= > L = ( R × A ) / ρ

Putting values here we get :

= > L = ( 10 × 6.25 π × 10⁻⁸ ) / 1.6 × 10⁻⁸  m

= > L =  62.5 π / 1.6

= > L = 122.72 m