Test: Heat (UPSC Level) - UPSC MCQ

We prefer wearing woolen clothes in winter because they keep us warm by providing insulation against the cold temperatures. On the other hand, light-colored cotton clothes are preferred in summer as they reflect light and heat, helping us stay cool. Woolen clothes trap air and prevent the body heat from escaping, while cotton allows the skin to breathe, making it suitable for warmer weather. It's essential to choose the right fabric based on the season to maintain comfort and regulate body temperature effectively.

1. Statement 1 is correct. Clinical thermometers are designed to measure body temperature, which typically ranges from 35°C to 45°C (or 94°F to 108°F). This reflects the normal range of human body temperatures and is consistent with the usage of clinical thermometers.

2. Statement 2 is incorrect. Digital thermometers do not use mercury. They are designed specifically to avoid the use of mercury due to its toxicity and environmental hazards. Instead, digital thermometers use electronic sensors to measure temperature, making them safer and more environmentally friendly than mercury-based thermometers.

3. Statement 3 is incorrect. The Fahrenheit scale is actually more sensitive than the Celsius scale. This is why body temperature is often measured in degrees Fahrenheit, as it allows for more precise readings within the typical range of human body temperatures. The statement incorrectly reverses the sensitivity of the scales.

Therefore, only Statement 1 is correct, making Option A: 1 Only the correct answer.

1. Clinical Thermometer - Measures air temperature: Incorrect. Clinical thermometers are specifically designed to measure the temperature of the human body, not air temperature.

2. Fahrenheit Scale - Freezing point of water at 0°F: Incorrect. The freezing point of water on the Fahrenheit scale is actually 32°F, not 0°F. The 0°F mark on the Fahrenheit scale is based on a brine solution.

3. Mercury Thermometer - Invented by Gabriel Fahrenheit: Correct. Gabriel Fahrenheit invented the mercury thermometer in 1714, marking a significant development in temperature measurement technology.

4. Digital Thermometer - Contains mercury for temperature measurement: Incorrect. Digital thermometers do not contain mercury. They use electronic sensors to measure temperature, which is safer and more environmentally friendly compared to mercury thermometers.

Based on the analysis, only one pair is correctly matched, which is the third pair: "Mercury Thermometer - Invented by Gabriel Fahrenheit."

Statement 1 is correct. Laboratory thermometers indeed have a Celsius scale ranging from -10°C to 110°C, allowing them to measure a wider range of temperatures than clinical thermometers, which typically range from 35°C to 42°C.

Statement 2 is correct. Laboratory thermometers are designed to measure a wider range of temperatures (from -10°C to 110°C) than clinical thermometers. This capability makes them suitable for various industrial applications where precise temperature measurements over a broader range are required.

Statement 3 is incorrect. Laboratory thermometers should not be tilted during use. For accurate readings, they must be placed upright, and readings should be taken only when the bulb is fully surrounded by the substance being measured.

Thus, statements 1 and 2 are correct, making Option B the correct answer.

Both statements are accurate. Statement-I highlights the usage and temperature range of laboratory thermometers, emphasizing their application in scientific environments. Statement-II provides additional details about the structural differences between laboratory and clinical thermometers, supporting the idea that laboratory thermometers can measure higher temperatures due to their extended stem and bulb. Therefore, Statement-II logically explains the context presented in Statement-I, making Option A the correct choice.

- Statement 1: This statement is incorrect. Conduction involves the transfer of heat without the movement of particles. In conduction, heat is transferred through direct contact between particles, but the particles themselves do not move to conduct the heat. This is typically observed in solids.

- Statement 2: This statement is correct. Convection involves the transfer of heat through the movement of fluids (liquids and gases). It occurs when warmer areas of a liquid or gas rise to cooler areas in the fluid, allowing heat to be transferred through the bulk movement of molecules.

- Statement 3: This statement is correct. Insulators are materials that do not allow heat to pass through them easily, while conductors are materials that facilitate the transfer of heat. Common examples of conductors include metals like copper and silver, and examples of insulators include wood and rubber.

Therefore, only statements 2 and 3 are correct. Hence, the correct answer is Option C: 2 and 3 Only.

Both statements, Statement-I and Statement-II, are correct. In conduction, heat is indeed transferred from the hotter part to the colder part without the movement of particles, while in convection, heat is transferred by the movement of particles from one place to another. Therefore, Statement-II explains the process of convection, which complements the definition of conduction provided in Statement-I.

Both Statement-I and Statement-II are accurate. Sea Breeze and Land Breeze phenomena are well-defined meteorological occurrences. Sea Breeze occurs when air over the sea is cooler than the air over the land during the day, leading to a breeze blowing from the sea towards the land. Conversely, Land Breeze happens at night when the land cools down faster than the water, causing a breeze from the land towards the sea. Statement-II explains the concept of Land Breeze following the same principle as Sea Breeze but in the opposite direction.

1. Woolen Clothes: Suitable for summer as they keep the body cool by trapping air. - Incorrect. Woolen clothes are not suitable for summer; they are used in winter because they trap air, providing insulation and retaining body warmth.

2. Light-colored Clothes: Preferred in summer for reflecting heat and keeping the body cool. - Correct. Light-colored clothes reflect sunlight and heat, helping keep the body cool in summer.

3. Cotton Clothes: Comfortable in summer as they absorb sweat and allow heat to escape. - Correct. Cotton is breathable and absorbs sweat, making it ideal for summer as it allows heat to dissipate.

4. Dark-colored Clothes: Preferred in winter for absorbing more heat and keeping the body warm. - Correct. Dark-colored clothes absorb more heat, making them suitable for winter as they help maintain body warmth.

Pairs 2, 3, and 4 are correctly matched. Therefore, three pairs are correctly matched, which is why the correct answer is Option C: Only three pairs.

Statement-I correctly explains the rationale behind wearing white or light-colored clothes in warm weather, as they reflect heat and aid in keeping the body cool. Statement-II is also accurate in highlighting the importance of wearing warm and thick dark clothes in cold weather, as they absorb heat effectively, leading to a sense of comfort. However, Statement-II does not directly explain or relate to Statement-I. Both statements independently address the appropriateness of clothing based on weather conditions without one statement necessarily elucidating the other. Hence, option (b) is the correct choice as both statements are correct but not interdependent.