A negligibly small current is passed though a wire of length 15m & resistance of  5Ω,having uniform cross section  of 6×10−7m2, then coefficient of resistivity of material is

# A negligibly small current is passed though a wire of length 15m & resistance of  $5\mathrm{\Omega },$having uniform cross section  of $6×{10}^{-7}{\mathrm{m}}^{2},$ then coefficient of resistivity of material is

1. A

$1×{10}^{-7}\mathrm{\Omega }-\mathrm{m}$

2. B

$2×{10}^{-7}\mathrm{\Omega }-\mathrm{m}$

3. C

$3×{10}^{-7}\mathrm{\Omega }-\mathrm{m}$

4. D

$4×{10}^{-7}\mathrm{\Omega }-\mathrm{m}$

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### Solution:

Length $\mathrm{l}=15\mathrm{m}\right]$ Resistance  $R=5\mathrm{\Omega }$
Cross sectional area  $\mathrm{A}=6×{10}^{-7}$

$\mathrm{\rho }=\frac{\mathrm{RA}}{\mathrm{l}}=\frac{5×6×{10}^{-7}}{15}\therefore \mathrm{\rho }=2×{10}^{-7}\mathrm{\Omega }-\mathrm{m}$

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