NEET Sample Paper NEET Sample Test Paper-76

  • question_answer
    The effective resistance of 'n' number of resistors when connected in parallel is A ohm. If one of the resistor is removed then the effective resistance becomes B ohm, then the resistance of resistor which is removed is

    A) \[\frac{AB}{B-A}\]                   

    B) \[\frac{AB}{A-B}\]

    C) \[\frac{A+B}{AB}\]                

    D) None of these

    Correct Answer: A

    Solution :

    When n resistors are connected in parallel, then \[\frac{1}{{{R}_{1}}}+\frac{1}{{{R}_{2}}}+....\,\,\,+\,\frac{1}{{{R}_{n-1}}}+\frac{1}{{{R}_{n}}}=\frac{1}{A}\]                        ... when nth resistor is removed, then \[\frac{1}{{{R}_{1}}}+\frac{1}{{{R}_{2}}}+....\,\,\,+\,\frac{1}{{{R}_{n-1}}}=\frac{1}{B}\]                ? Subtracting  from , we get \[\frac{1}{{{R}_{n}}}=\frac{1}{A}-\frac{1}{B}\,\,\Rightarrow \,\,\,{{R}_{n}}=\frac{AB}{B-A}\]


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