UPSC Prelims 2010 · General Studies

Question 88: Science and Technology

What is the principle by which a cooling system (Radiator) in a motor car works ?

aConduction only

bConvection

cRadiation only

dBoth conduction and radiation

AnswerThe answer is (b).

A car radiator removes engine heat by circulating coolant. The liquid carries heat from the engine to the radiator by convection currents (driven by a pump), and air moving across the radiator's fins carries the heat away from the metal surface, also by convection. Conduction through the metal and radiation play only supporting roles. Remember: heat carried by a moving fluid = convection.

Why each option is right or wrong

(a) Conduction occurs in the metal walls but is not the main principle.
(b) Right: moving coolant and moving air carry the heat by convection.
(c) Radiation is a minor contributor.
(d) Neither conduction nor radiation is the main principle.

Explanation: written by UPSC Grade, not by UPSC.

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Source: UPSC, Civil Services (Preliminary) Examination 2010, General Studies, Series A. The paper on upsc.gov.in.