12th Class Physics Alternating Current / प्रत्यावर्ती धारा Question Bank Assertion And Reason (MCQs) - Alternating Currents

  • question_answer
    Directions: In the following questions, a statement of Assertion [A] is followed by a statement of Reason (R).
    Mark the correct choice as:
    Assertion [A]: AC is more dangerous than DC.
    Reason (R): Frequency of AC is dangerous for human body.

    A) Both Assertion [A] and Reason (R) are true and Reason (R) is the correct explanation of Assertion [A]        

    B) Both Assertion [A] and Reason (R) are true but Reason (R) is not the correct explanation of Assertion [A]

    C) Assertion [A] is true but Reason (R) is false

    D) Assertion [A] is false and Reason (R) is also false

    Correct Answer: A

    Solution :

    (a) The effect of AC on the body depends largely on the frequency. Low frequency currents of 50 to 60 Hz (cycles/sec), which are commonly used, are usually more dangerous than high frequency currents and are 3 to 5 times more dangerous than DC of same voltage of amperage (current). The usual frequency of 50 cps (or 60 cps) is extremely dangerous as it corresponds to the fibrillation frequency of the myocardium. This results in ventricular fibrillation and instant death.


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