NEET-XII-Physics
32: Electric Current in Conductors
- #11-aHow many electrons are transferred per second between the supply and the wire at one end? (b) Write down the current density in the wire.Ans : Let q be the charge transferred per second and n be the number of electrons transferred per second.
We know:
`` i=\frac{V}{R}``
`` \Rightarrow i=\frac{20\,\mathrm{\,V\,}}{{10}^{3}\,\mathrm{\,\Omega \,}}``
`` \Rightarrow i=20\times {10}^{-3}=2\times {10}^{-2}\,\mathrm{\,A\,}``
`` q\mathit{=}it``
`` \Rightarrow q=2\times {10}^{-2}\times 1``
`` \Rightarrow q=2\times {10}^{-2}\,\mathrm{\,C\,}``
Also,
q = ne
`` \Rightarrow n=\frac{q}{e}=\frac{2\times {10}^{-2}}{1.6\times {10}^{-19}}``
`` \Rightarrow n=1.25\times {10}^{17}`` (b) Current density of a wire,
`` j=\frac{i}{A}``
`` \Rightarrow j=\frac{2\times {10}^{-2}}{3.14\times {10}^{-8}}``
`` \Rightarrow j=6.37\times {10}^{5}\,\mathrm{\,A\,}/{\,\mathrm{\,m\,}}^{2}``
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- #11-bWrite down the current density in the wire.Ans : Current density of a wire,
`` j=\frac{i}{A}``
`` \Rightarrow j=\frac{2\times {10}^{-2}}{3.14\times {10}^{-8}}``
`` \Rightarrow j=6.37\times {10}^{5}\,\mathrm{\,A\,}/{\,\mathrm{\,m\,}}^{2}``
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