Question

A 20m length wire 1.5mm in diameter has a resistance of 2.5 ohm what is the resistance of a 35m length of wire 3mm in diameter made of the same material?​

Answer 1

From the calculations, the resistance of the material is 1.1 ohm.

What is the resistance of the wire?

Given that;

R α l/A

R = ρl/A

R = resistance

l = length

A = Area

ρ = resistivity

Now;

A = πr^2

A = 3.142 * (1.5 * 10^-3/2)^2

A = 1.77 * 10^-6 m^2

ρ = RA/l

ρ =  2.5 *  1.77 * 10^-6 /20

ρ = 2.2 * 10^-7 ohm/m

Now;

R =ρl/A

A =  3.142 * (3  * 10^-3/2)^2

A = 7.1 * 10^-6 m^2

Thus

R = 2.2 * 10^-7 * 35/ 7.1 * 10^-6

R = 1.1 ohm

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