Question

The area of cross-section of a metallic wire is 4×10⁻⁸ m² and it's specific resistance is 10× 10⁻⁸ Ohm meter. If the resistance of wire is 25 Ohm , what would be it's length ?

a) 2m

b) 5m

c) 10m

d) 20m


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Answer 1

Answer:

L = 10m

Explanation:

Given:

Area of the cross-section of the wire (A) = 4 × 10⁻⁸ m²

Resistivity (ρ) = 10 × 10⁻⁸ Ωm

Resistance (R)= 25Ω

Length of the wire (L)=?

Now,

R = ρ × L/A

⇒L = R × A/ρ

⇒L = 25 × 4 × 10⁻⁸/10 × 10⁻⁸

⇒L = 25 × 4/10 (10⁻⁸ ÷ 10⁻⁸ = 1)

⇒L = 100/10

⇒L = 10m

Answer 2

length of a metallic wire is 10m

Explanation:

Given:

Area of the cross-section of the wire (A) = 4 × 10⁻⁸ m²

Resistance of wire (R)= 25Ω

specific Resistivity (ρ) = 10 × 10⁻⁸ Ωm

To Find:

Length of the wire (L)

Explanation:

L = R × A/ρ

= 25 × 4 × 10⁻⁸/10 × 10⁻⁸

= 25 × 4/10 (10⁻⁸ ÷ 10⁻⁸ = 1)

= 100/10

L = 10m

hence, length of a metallic wire is 10m