CET Karnataka Engineering CET - Karnataka Engineering Solved Paper-2003

  • question_answer
    A group of N cells whose emf varies directly with the internal resistance as per the equation \[{{E}_{N}}=1.5\,{{r}_{N}}\] are connected as shown in the figure above. The current I in the circuit is:

    A)  5.1 A                    

    B)  0.51 A

    C)  1.5 A                    

    D)  0.15 A

    Correct Answer: C

    Solution :

    Given that emf \[{{E}_{N}}=1.5\,{{r}_{N}}\] where \[{{r}_{N}}\] is the internal resistance of nth cell. Total emf \[E={{E}_{1}}+{{E}_{2}}+{{E}_{3}}+....+{{E}_{n}}\]                 \[=1.5\,[{{r}_{1}}+{{r}_{2}}+{{r}_{3}}+....+{{r}_{n}}]\] Total internal resistance                 \[r={{r}_{1}}+{{r}_{2}}+{{r}_{3}}+....\,{{r}_{n}}\] \[\therefore \] current \[i=\frac{{{E}_{total}}}{{{r}_{total}}}\]              \[i=\frac{1.5\,\,[{{r}_{1}}+{{r}_{2}}+{{r}_{3}}+\,...\,+{{r}_{n}}]}{[{{r}_{1}}+{{r}_{2}}+{{r}_{3}}+\,...\,+{{r}_{n}}]}\] Hence,  \[i=1.5\,\,A\]


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