12th Class Physics Alternating Current / प्रत्यावर्ती धारा Question Bank Case Based (MCQs) - Alternating Current

  • question_answer
    In a transformer the number of primary turns is four times that of the seconary turns. Its primary is connected to an a. c. source of voltage V. Then

    A) current through its seconary is about four times that of the current through its primary

    B) voltage across its secondary is about four times that of the voltage across its primary

    C) voltage across its seconary is about two times that of the voltage across its primary

    D) voltage across its seconary is about \[\frac{1}{2\sqrt{2}}\] times that of the voltage across its primary.

    Correct Answer: A

    Solution :

    In a transformer the primary and secondary currents are related by \[{{I}_{s}}=\left( \frac{{{N}_{p}}}{{{N}_{s}}} \right){{I}_{p}}\] and the voltages are related by \[{{V}_{s}}=\left( \frac{{{N}_{s}}}{{{N}_{p}}} \right){{V}_{p}}\] where subscripts p and s refer to the primary and secondary of the transformer. Here \[{{V}_{p}}=V,\,\frac{{{N}_{p}}}{{{N}_{s}}}=4\] \[\therefore \,\,\,{{I}_{s}}=4{{I}_{p}}\] \[\therefore \,\,{{I}_{s}}=4{{I}_{p}}\] And \[{{V}_{s}}=\frac{1}{4}V=\frac{V}{4}\]


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