12th Class Physics Alternating Current / प्रत्यावर्ती धारा Question Bank MCQ - Alternating Currents

  • question_answer
                         In an AC circuit, V and l are given by \[V=150\,\sin \,(150t)V\] and \[l=150\,\sin \,\left( 150\,t+\frac{\pi }{3} \right)A\]. The power dissipated in the circuit is:

    A) 106 W             

    B) 150 W

    C) 5625 W                        

    D) zero  

    Correct Answer: C

    Solution :

    (c) 5625 W Compare \[V=150\,\sin \,(150\,t)\]with \[V={{V}_{0}}\sin \,\omega t\]. we get, \[{{V}_{0}}=150\,V\] Compare \[l=150\,\sin \left( 150t+\frac{\pi }{3} \right)\] with \[l={{l}_{0}}\sin \,(\omega t+\phi )\]. we get   \[{{l}_{0}}=150\,A,\,\phi =\frac{\pi }{3}=60{}^\circ \] The power dissipated in AC circuit is \[P=\frac{1}{2}{{V}_{0}}{{l}_{0}}\cos \,\phi =\frac{1}{2}\times 150\times 150\times \cos \,60{}^\circ \] \[=\frac{1}{2}\times 150\times 150\times \frac{1}{2}=5625\,W\]


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