Physics 2015 JAMB Past Questions - Question 18: the resistance of a piece of wire of length 20m are cross sectional area of 8x10^6m[Resistivity of the wire = 4 x 10-7 Ω m]

Correct Answer

A

Explanation

To calculate the resistance of a wire, we need to use the formula:

Resistance (R) = Resistivity (ρ) x Length (L) / Cross-sectional Area (A)

Given:
Length (L) = 20 m
Cross-sectional Area (A) = 8 x 10^6 m^2
Resistivity (ρ) = 4 x 10^-7 Ω m

Let's substitute these values into the formula:

Resistance (R) = (4 x 10^-7 Ω m) x (20 m) / (8 x 10^6 m^2)

Simplifying the expression:

Resistance (R) = (4 x 20) / (8 x 10^6) Ω
Resistance (R) = 80 / 8 x 10^6 Ω
Resistance (R) = 10 x 10^-6 Ω
Resistance (R) = 10 μΩ

Therefore, the resistance of the wire is 10 microohms (μΩ).