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10th Class Science Electricity and Circuits Question Bank Electricity

  • question_answer
    An electric heater has resistance 150 ohms and can bear a maximum current of 1 ampere. If the heater is to be used on 220 volt mains, the least resistance required in the circuit will be

    A)  70 ohms               

    B)  5 ohms

    C)  \[2.5\] ohms        

    D)         \[1.4\] ohms

    Correct Answer: A

    Solution :

     If \[200\,\,V\] is supplied to a resistance of \[150\Omega \], current supplied\[=\frac{220}{150}\]. This is greater than the maximum current the heater can withstand. So, resistance of the circuit should be increased Now,     \[1=\frac{220}{150+R}\]or            \[R=70\Omega \]


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