CET Karnataka Medical CET - Karnataka Medical Solved Paper-2007

  • question_answer
    An electric bulb has a rated power of 50 W at 100 V. If it is used on an AC source 200 V, 50 Hz, a choke has to be used in series with it. This choke should have an inductance of

    A)  0.1 mH

    B)  1 mH

    C)  0.1 H

    D)  1.1 H

    Correct Answer: D

    Solution :

    Resistance of bulb \[R=\frac{{{V}^{2}}}{P}=\frac{{{(100)}^{2}}}{50}\] \[=200\Omega \] Current through bulb (I) \[=\frac{V}{R}\] \[=\frac{100}{200}=0.5A\] In a circuit containing inductive reactance \[({{X}_{L}})\]and resistance (R), impedance (Z) of the circuit is \[Z=\sqrt{{{R}^{2}}+{{\omega }^{2}}{{L}^{2}}}\] ...(i) Here,           \[Z=\frac{200}{0.5}=400\Omega \] Now       \[X_{L}^{2}={{Z}^{2}}-{{R}^{2}}\] \[={{(400)}^{2}}-{{(200)}^{2}}\] \[{{(2\pi fL)}^{2}}=12\times {{10}^{4}}\] \[L=\frac{2\sqrt{3}\times 100}{2\pi \times 50}\] \[=\frac{2\sqrt{3}}{\pi }=1.1H\]


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