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
Correct Answer: Option B
Explanation
R = (frac{4eL}{pid^2})
L = (frac{Rpid^2}{4e})
= (frac{21 times 3.14(4 times 10^{-3})^2}{4 times 3.0 x 10^{-8}})
= 8.8 x 103m