An aluminium cable of diameter 4 x 10-3m and resistivity 3.0 x 10-8\(\omega\)m has a resistance of 21\(\Omega\). Calculate the length of the cable. (\(\pi = 3.14\))
A
8.0 x 102m
B
8.8 x 103m
C
8.0 x 104m
D
8.8 x 104m
Verified Correct Answer: B.
Physical Principles & Numerical Solution
R = \(\frac{4eL}{\pid^2}\)
L = \(\frac{R\pid^2}{4e}\)
= \(\frac{21 \times 3.14(4 \times 10^{-3})^2}{4 \times 3.0 x 10^{-8}}\)
= 8.8 x 103m
Source: Myschool Past Questions Archive (Record #45652)