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Question

Physics Question on Current electricity

Dimensions of a block are 1cm1cm100cm1\,cm � 1\,cm � 100\,cm. If specific resistance of its material is 3×107Ωm3\times 10^{-7} \,\Omega\, m, then the resistance between the opposite rectangular faces is

A

3×107Ωm3\times 10^{-7} \,\Omega\, m

B

3×109Ωm3\times 10^{-9} \,\Omega\, m,

C

3×105Ωm3\times 10^{-5} \,\Omega\, m,

D

3×103Ωm3\times 10^{-3} \,\Omega\, m,

Answer

3×107Ωm3\times 10^{-7} \,\Omega\, m

Explanation

Solution

Here length l=1cm=102ml=1\,cm=10^{-2}\,m

Area of cross-section, A=1cm×100cmA = 1\,cm\times100\,cm
=100cm2= 100 \,cm^{2}
=102m2=10^{-2}\,m^{2}
Resistance, R=ρA=3×107×102102R=\rho \frac{\ell}{A}=3\times10^{-7}\times\frac{10^{-2}}{10^{-2}}
=3×107Ω=3\times10^{-7}\,\Omega