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NEET Sample Paper NEET Sample Test Paper-79

  • question_answer
    When a current I flows through a wire, the drift velocity of the electron is v. When current 2I flows through another wire of the same material having double the length and double the area of cross-section, the drift velocity of the electrons will be

    A)  \[\frac{v}{8}\]                         

    B)  \[\frac{v}{4}\]

    C)  \[\frac{v}{2}\]                         

    D)  v

    Correct Answer: D

    Solution :

    \[I=neA{{v}_{d}}\] \[{{v}_{d}}=\frac{I}{neA}\] \[\Rightarrow \,\,\,\,\,\,\,\,{{v}_{d}}\propto \frac{I}{A}\] \[\therefore \,\,\,\,\,\,\,\,\,\,\,\,\frac{{{v}_{d}}'}{{{v}_{d}}}=\,\,\frac{I'/A'}{I/A}=\,\,\frac{2I/2A}{I/A}=1\] or   \[{{v}_{d}}^{'}={{v}_{d}}=v\]


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