Question

The diagram shows two air filled bulbs connected by a U-tube partly filled with a low density (or light) oil. How the levels of oil in the limbs X and Y change after the electric bulb is lighted

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• A. The level of oil in limb X limb and Y rises or falls to the same extent.
• B. There is no observable change.
• C. The level of oil in limb X falls while in limb Y, the level of oil rises.
• D. The level of oil in limb X rises while in limb Y, the level of oil falls.

Answer 1

The correct option is C

The level of oil in limb X falls while in limb Y, the level of oil rises.

Black bulb absorbs heat, so air inside expands and pushes down the oil of limb X which passes to the limb Y.