Question

Length of the wite is 50cm and radius 0.5mm find the resistivity of wire if wire if its resistance is 30hm

Answer 1

we know that r=resistivity *l/A
where R is Resistance l is the length of wire and a is the cross sectional area

hence,resistivity = r*A/l

now, length is 50/100=0.5m and radius is 5*10^-4 m

so, resistivity = (30*(22/7*(5*10^-4)*(5*10^-4)))/0.5

=(30*(22/7*(25*10^-8))/0.5

=(30*(78.5*10^-8))/0.5

=(2355*10^-8)/0.5

=4710*10^-8 ohm/cm

Answer 2

R = ρl/A 

ρ = R x A / l 

ρ = 30 x 3.14 x 0.5 x 10⁻³  x 0.5 x 10⁻³ / 50 x 10⁻²

ρ = 23.55 x 10⁻⁶ x 10² / 50 

ρ = 23.55 x 10⁻⁴ / 50 

ρ = 0.471 x 10⁻⁴

ρ = 4.71 x 10⁻⁵ ohm/cm