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Current Electricity question

2022 · Q155
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Current Electricity question

2022 · Q155

NEETPhysicsCurrent ElectricityMCQ+4 / −1

A copper wire of length 10 m and radius (10−2π)\left( {{{{{10}^{ - 2}}} \over {\sqrt \pi }}} \right)(π​10−2​) m has electrical resistance of 10 Ω\OmegaΩ. The current density in the wire for an electric field strength of 10 (V/m) is

  1. A
    104 A/m2
  2. B
    106 A/m2
  3. C
    10−-−5 A/m2
  4. D
    105 A/m2
View written solutionFree

Correct answer: D

Resistance, $$R = \rho {L \over A} = {L \over {\sigma A}}$$

$$ \Rightarrow \sigma = {L \over {RA}}$$

Also current density $$j = \sigma E = {{LE} \over {RA}}$$

$$J = {{10 \times 10} \over {10 \times \pi {{\left( {{{{{10}^{ - 2}}} \over {\sqrt \pi }}} \right)}^2}}} = {{100} \over {10 \times \pi \times \left( {{{{{10}^{ - 4}}} \over \pi }} \right)}}$$

$ = {10^5}$ A/m2

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