Question

calculate the resistance of a constantan wire of length 2.0 M and radius 0.1 millimetre given the resistivity of constantan is 49 * 10^-8 ohm/metre

Answer 1

apply R = rho. L/A
A = π r^2
r= 0.1 mm ,convert it into m
L= 2 m
rho = 49.10^ -8 ohm/ m
you will get resistance as 31.1 ohm

Answer 2

Answer:31.181

Explaination

Roh =RA/L

=> R=roh×L/A

and A=pi r^2

Given that, L=2.0m

r=0.1mm =1×10^-4m

roh= 49×10^-8 ohmm

Now, R=(49×10^-8 ×2) / ((22/7) ×(10^-4)^2)

or R= 49×2×7×10^-8/22×10^-8

or R=49×2×7/22

or R=49×7/11

Or R=343/11

Or

R= 31.181 ohm

Answer