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CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2003

  • question_answer
    If a transformer of an audio amplifier has output impedance\[8000\,\Omega \]and the speaker has input impedance of \[8\Omega \], the primary and secondary turns of this transformer connected between the output of amplifier and to loud speaker should have the ratio:

    A)  \[1000:1\]                          

    B)  \[100:1\]            

    C)         \[1:32\]              

    D)         \[32:1\]

    E)  \[1:1000\]

    Correct Answer: C

    Solution :

    Output power = input power i.e.,        \[{{V}_{s}}{{I}_{s}}={{V}_{p}}{{I}_{p}}\] or            \[I_{s}^{2}{{R}_{out}}=I_{2}^{2}{{R}_{in}}\] or            \[\sqrt{\left( \frac{{{R}_{out}}}{{{R}_{in}}} \right)}=\frac{{{I}_{p}}}{{{I}_{s}}}\]                    ?.. (1) Also,         \[\frac{{{I}_{p}}}{{{I}_{s}}}=\frac{{{N}_{s}}}{{{N}_{p}}}\]                             ...(2) \[\therefore \]\[\frac{{{N}_{P}}}{{{N}_{s}}}=\sqrt{\left( \frac{{{R}_{in}}}{{{R}_{out}}} \right)}=\sqrt{\left( \frac{8}{8000} \right)}=\frac{1}{10\sqrt{10}}\] \[=1:32\]


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