JEE Main & Advanced Physics Electrostatics & Capacitance Question Bank Electric Field and Potential

  • question_answer
    Infinite charges of magnitude q each are lying at x =1, 2, 4, 8... meter on X-axis. The value of intensity of electric field at point x = 0 due to these charges will be   [J & K CET 2004]

    A)            \[12\times {{10}^{9}}q\text{ }N/C\]                              

    B)            Zero

    C)            6 ´ 109q N/C

    D)                                      4 ´ 109q N/C

    Correct Answer: A

    Solution :

                 Net field at origin \[E=\frac{q}{4\pi {{\varepsilon }_{0}}}\left[ \frac{1}{{{1}^{2}}}+\frac{1}{{{2}^{2}}}+\frac{1}{{{4}^{2}}}+....\infty  \right]\] \[=\frac{q}{4\pi {{\varepsilon }_{0}}}\left[ 1+\frac{1}{4}+\frac{1}{16}+.....\infty  \right]\] \[=\frac{q}{4\pi {{\varepsilon }_{0}}}\left[ \frac{1}{1-\frac{1}{4}} \right]=12\times {{10}^{9}}q\,N/C\]


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