Punjab Medical Punjab - MET Solved Paper-2011

  • question_answer
    In the given circuit if point\[C\]is connected to the earth and a potential of\[+2000\,\,V\]is given to the point\[A\], the potential at\[B\]is

    A) \[1500\,\,V\]                     

    B) \[1000\,\,V\]

    C) \[500\,\,V\]                       

    D) \[400\,\,V\]

    Correct Answer: C

    Solution :

    The equivalent capacity of\[10\,\,\mu F\]and\[10\mu F\]capacitors connected in series                 \[{{C}_{1}}=\frac{10\times 10}{10+10}=5\mu F\] Now equivalent capacitance between\[B\]and\[C\]which are connected in parallel                 \[{{C}_{2}}=5+10=15\mu F\] Total capacitance of the circuit between\[A\]and\[C\]when\[{{C}_{2}}\] and\[5\mu F\]are connected in series.                 \[{{C}_{3}}=\frac{5\times 15}{5+15}=\frac{15}{4}\mu F\] \[\therefore \]  \[Q={{C}_{3}}V=\frac{15}{4}\times 2000=7500\mu C\] Potential difference across\[A\]and\[B\]                 \[{{V}_{AB}}=\frac{7500}{5}\] \[i.e.,\] \[{{V}_{A}}-{{V}_{B}}=1500\,\,V\] \[\therefore \]\[2000-{{V}_{B}}=1500\]or\[{{V}_{B}}=500\,\,V\]


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