2. Solved Papers
  3. CET Karnataka Engineering

CET Karnataka Engineering CET - Karnataka Engineering Solved Paper-2006

  • question_answer
    A 30 V, 90 W lamp is to be operated on a 120 V DC line. For proper glow, a resistor of ...... \[\Omega \] should be connected in series with the lamp.

    A)  40                                         

    B)  10

    C)  20                                         

    D)  30

    Correct Answer: D

    Solution :

    Resistance of the lamp                 \[{{R}_{0}}=\frac{{{V}^{2}}}{p}\]                 \[=\frac{{{(30)}^{2}}}{90}=10\,\,\Omega \] Current in the lamp                 \[i=\frac{30}{10}=3\,\Omega \] When lamp is operated on a 120 y then resistance                 \[R=\frac{V}{i}=\frac{120}{3}=40\,\,\Omega \] Thus, for proper glow, the resistance required to the put in series will be                 \[R=R-{{R}_{0}}=40-10=30\Omega \]


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