The correct option for the question "The heat required to raise the temperature of the body by 1k is called?" is **B. Thermal capacity**. ### Detailed Explanation: 1. **Understanding the Terms**: - **Specific Heat**: This is defined as the amount of heat required to raise the temperature of 1 gram of a substance by 1 degree Celsius (or 1 Kelvin, since the size of the degree is the same in both scales). It is a property of the material and is usually expressed in units of J/(g·K). - **Thermal Capacity**: Also known as heat capacity, this is the amount of heat required to raise the temperature of an entire object (not just a unit mass) by 1 degree Celsius (or 1 Kelvin). It is an extensive property, meaning it depends on the size or amount of the material, and is expressed in joules per Kelvin (J/K). - **Water Equivalent**: This term refers to the mass of water that would absorb the same amount of heat as a given body for a given temperature change. It is not directly related to the heat required to raise the temperature of a body by 1K. - **None of the Above**: This option implies that none of the provided answers are correct, which is not the case here. 2. **Why Option B is Correct**: - The question specifically asks for the heat required to raise the temperature of a body by 1K. This definition aligns perfectly with the concept of thermal capacity (or heat capacity). When we say "the heat required to raise the temperature of the body by 1K," we are essentially describing the heat capacity of that body. 3. **Why the Other Options are Incorrect**: - **Option A (Specific Heat)**: While specific heat is related to the heat required to raise the temperature, it is specific to a unit mass of the substance. The question refers to the entire body, not just a unit mass, making this option incorrect. - **Option C (Water Equivalent)**: This term does not describe the heat required to raise the temperature of a body. Instead, it is a comparative measure that relates to how much heat a body can absorb compared to water. Therefore, it does not fit the definition provided in the question. - **Option D (None of the Above)**: Since we have identified that option B is indeed correct, this option is also incorrect. ### Summary of Key Concepts: - **Thermal Capacity**: The total heat required to raise the temperature of an entire object by 1K. - **Specific Heat**: The heat required to raise the temperature of 1 gram of a substance by 1K; it is a property of the material. - **Water Equivalent**: A measure of heat capacity in terms of the mass of water that would absorb the same amount of heat. - **Heat Capacity** is an extensive property, while specific heat is an intensive property. ### Revision Summary: - The heat required to raise the temperature of a body by 1K is called **Thermal Capacity** (Option B). - **Specific Heat** applies to unit mass, not the entire body. - **Water Equivalent** is a comparative measure, not a direct definition of heat capacity. - Understanding the distinction between thermal capacity and specific heat is crucial for solving related problems in thermodynamics.