2. Solved Papers
  3. Haryana PMT

Haryana PMT Haryana PMT Solved Paper-2002

  • question_answer
    The electrical cable of copper has just one wire of radius 9 mm its resistance is 10\[\Omega \]. This single copper wire is replaced by 3 different well insulated copper wires each of radius 3 mm. The total resistance of the cable will now be equal to :

    A)  90 \[\Omega \]               

    B)  45 \[\Omega \]

    C)  30 \[\Omega \]               

    D)  15 \[\Omega \]

    Correct Answer: C

    Solution :

                    Resistance of the wire \[R\propto \frac{1}{{{r}^{2}}(radius)}\] Radius of new wire is \[\frac{1}{3}rd\] of the initial wire. its resistance \[R=10{{(3)}^{2}}\]                                 \[=10\times 9\]                                 \[=90\Omega \] Now total resistance of all the 3 wires in parallel \[=\frac{90}{3}=30\Omega \]


You need to login to perform this action.
You will be redirected in 3 sec spinner