J & K CET Engineering J and K - CET Engineering Solved Paper-2005

  • question_answer
    The plates of a charged condenser are connected to a voltmeter. If the plates are moved apart, the reading of voltmeter will

    A)  increase

    B)  decrease

    C)  remain unchanged

    D)  information is insufficient

    Correct Answer: A

    Solution :

    The capacitance  of a capacitor is defined as the ratio of the charge (q) given to the rise in the potential (V) of the conductor. When the plates are moved apart, the charge remains constant, hence \[q=CV=\]constant            ??.(i) Capacitance  of a parallel plate capacitor is given by \[C=\frac{{{\varepsilon }_{0}}A}{d}\] ?..(ii) where A is area of plates and d the separation  between them.                             From Eqs. (i) and (ii), we have \[q=\frac{{{\varepsilon }_{0}}A}{d}.V=\text{constant}\] When plates are moved apart, d increases, hence value of C decreases and in order that charge (q) remains constant V increases.


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