# Chapter 1:Materials Properties and Requirements¶

## Example 1.1, page no-8¶

In [1]:
#Resistance of the wire

import math
#variable declaration
r=0.45*10**-3           # radius of the wire
L=0.3                   # length of the wire
rho=17.0*10**-9         # resistivity of wire in ohm-m

#Calculations
R=rho*(L/(math.pi*r**2))

#Result
print('The resistance of the wire is %.3f ohm'%R)

The resistance of the wire is 0.008 ohm


## Example 1.2, page no-8¶

In [4]:
#Extension of a wire

import math
#variable declaration
r=1.25*10**-3         # radius of the wire in m
L=3.0                 # length of wire in m
F=4900.0              # applied force in Newton
e=2.05*10**11         # modulus of elasticity

#calculation
s=F/(math.pi*r**2*e)

#result
print('strain = %.3f\nTherefore, extension = %.3f m'%(s,s*3))

strain = 0.005
Therefore, extension = 0.015 m