An aluminium cable of diameter 4 x 10 -3 m and resistivity 3.0 x 10
PHYSICS
WAEC 2016
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: B. 8.8 x 103m
Explanation
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
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