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

  • question_answer
    Direction: Q.11 to Q.15
    The power averaged over one full cycle of AC is known as average power. It is also known as true power. \[{{P}_{av}}={{V}_{rms}}{{I}_{rms}}\cos \phi =\frac{{{V}_{0}}{{I}_{0}}}{2}\cos \phi \].
    Root mean square or simply rms watts refer to continuous power.
    A circuit containing a 80 mH inductor and a \[60\text{ }\mu F\] capacitors in series is connected to a 230 V, 50 Hz supply. The resistance of the circuit is negligible.
    Read the above passage carefully and give the answer of the following questions:
    The value of current amplitude is:

    A) 15 A                            

    B) 11.63 A  

    C) 17.65 A                        

    D) 6.33 A

    Correct Answer: B

    Solution :

    (b) 11.63 A Inductance, \[L=80\text{ }mH=80\times {{10}^{-3}}H\] Capacitance, \[C=60\,\mu F=60\times {{10}^{-6}}F,V=230\,V\] Frequency, \[v=50\text{ }Hz\] \[\omega =2\pi v=100\,\pi \,\,rad\,{{s}^{-1}}\] Peak voltage, \[{{V}_{0}}=V\sqrt{2}=230\,\sqrt{2}\,V\] Maximum current is given by, \[{{l}_{0}}=\frac{{{V}_{0}}}{\left( \omega L-\frac{1}{\omega C} \right)}\] \[{{l}_{0}}=\frac{230\sqrt{2}}{\left( 100\pi \times 80\times {{10}^{-3}}-\frac{1}{100\pi \times 60\times {{10}^{-6}}} \right)}\] \[{{l}_{0}}=\frac{230\sqrt{2}}{\left( 8\pi -\frac{1000}{6\pi } \right)}=-11.63\,A\] Amplitude of maximum current, \[{{\text{l}}_{0}}=11.63\text{ }A\]


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