Question 11:
easyAssertion (A): Temperature near the sea-coast are moderate.
Reason (R): Water has a high thermal conductivity.
Coastal temperatures are moderate because water has a high specific heat capacity, absorbing and releasing large amounts of heat without significant temperature change.
Water's thermal conductivity is not high. Thus, R is false.
Question 12:
easyAssertion (A): Most of the heat transfer that is taking place on earth is by convection.
Reason (R): Mostly heat radiation from sun are obtained in infrared region.
Within the Earth's atmosphere and oceans, convection is indeed the primary mechanism for heat distribution, making Assertion (A) true. However, the Sun's peak radiation is in the visible light spectrum (around `\(500\text{ nm}\)`), not predominantly in the infrared region. Therefore, Reason (R) is false.
Question 13:
easyAssertion (A): Conduction usually takes place in solids, convection in liquids and gases and no medium is required for radiation.
Reason (R): In conduction and convection, heat is transferred from one place to other by actual motion of heated material.
Assertion (A) correctly describes the primary media for each mode of heat transfer: conduction in solids, convection in fluids (liquids and gases), and radiation requiring no medium. So, (A) is true. Reason (R) is false because in conduction (especially in solids), heat is transferred by molecular vibrations and collisions, not by the actual bulk motion of heated material. Bulk motion is characteristic of convection.
Question 14:
easyAssertion (A): When temperature difference across the two sides of a wall is increased, its thermal conductivity increases.
Reason (R): Thermal conductivity depends upon the temperature difference across the two sides of a wall.
Thermal conductivity is an intrinsic property of the material and does not depend on temperature difference. It depends on the material itself and its temperature. Both assertion (A) and reason (R) are incorrect statements. Hence, option (4) is correct.
Question 15:
easyAssertion (A): Specific heat of a body may be greater than its thermal capacity.
Reason (R): Mass of a body may be less than unity.
Thermal capacity is \(C = mc\), where \(m\) is mass and \(c\) is specific heat. If \(m < 1\) (e.g., in kg), then \(c\) will be numerically greater than \(C\). Thus, (A) is true. (R) states mass can be less than unity, which is true and correctly explains (A).