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7th Class Science Heat Question Bank Heat

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    DIRECTIONS: On the basis of following diagram/ picture answer the questions given below: The figure shows air-filled bulbs connected by a U-tube partly filled with alcohol. What happens to the levels of alcohol in the limbs X and Y when an electric bulb is placed midway between the painted air filled bulbs and electric bulb is lighted?

    A) The level of alcohol falls in both limbs.

    B) The level of alcohol in the limb X rises while that in limb Y falls.

    C) The level of alcohol in limb X falls while that in limb Y rises.

    D) There is no change in the levels of alcohol in the two limbs.

    Correct Answer: C

    Solution :

        Black color being a better absorber of heat, bulb X gets more heated due to heat radiated by the electric bulb resulting in me expansion of air inside it. The expanded air requires more space and thus pushes me alcohol towards limb Y.          


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