10th Class Science Electricity and Circuits Question Bank Electricity

  • question_answer
    How will be the reading in the ammeter A affected if another identical bulb Q is connected in parallel to P? (The voltage in the mains is maintained at a constant value.)

    A) The reading will be reduced to one-half.

    B) The reading will not be affected.

    C) The reading will be doubled.

    D) The reading will be increased four-fold.

    Correct Answer: C

    Solution :

    Let, resistance of bulb P and Q be R. So reading of ammeter before connecting Q to the circuit is \[I=\frac{V}{R}\]                                                           ?.(i) After connecting Q to the circuit, resultant resistance of the circuit is \[\frac{1}{{{R}_{eq}}}=\frac{1}{R}+\frac{1}{R}=\frac{2}{R}\]or \[{{R}_{eq}}=\frac{R}{2}\Omega \] Thus, new reading of ammeter will be \[l'=\frac{V}{R/2}=\frac{2V}{R}\] or         \[l'=2l\]                          (From (i))


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