CET Karnataka Medical CET - Karnataka Medical Solved Paper-2003

  • question_answer
    A charge q is placed at the centre of the line joining two equal point charges each equal to Q. The system of 3 charges will be in equilibrium if q is equal to:

    A)  + Q / 4

    B)  - Q / 2

    C)  + Q / 2

    D)  - Q / 4

    Correct Answer: D

    Solution :

    For equilibrium of system of charges force produced between q and Q+ force produced between Q and Q = 0 \[\frac{1}{4\pi {{\varepsilon }_{0}}}\frac{qQ}{{{(r/2)}^{2}}}+\frac{1}{4\pi {{\varepsilon }_{0}}}\frac{QQ}{{{r}^{2}}}=0\] \[\Rightarrow \]   \[\frac{4qQ}{{{r}^{2}}}+\frac{QQ}{{{r}^{2}}}=0\] \[\Rightarrow \]    \[q=-\frac{Q}{4}\]


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