Test: Heat and Thermodynamics - SSC CGL MCQ

Heat is a form of energy that generates the sensation of warmth in objects. It flows from hotter objects to cooler ones as a result of temperature differences. When a body is heated, it can undergo various changes, such as expansion, contraction, changes in state, and alterations in electrical properties. This energy transfer is crucial in various applications, from everyday experiences like cooking to more complex scientific processes like thermal engineering.

Heat is typically measured in joules, which is the standard unit of measurement for this form of energy. The calorie is also commonly used to quantify heat energy, with 1 calorie equivalent to 4.2 joules. Understanding these units is important for calculating and comparing heat transfer in various systems, whether in daily activities like cooking or in complex industrial processes.

Heat energy always flows from hotter objects to cooler ones due to the temperature difference between them. When heat is transferred between bodies, it can be converted into various other forms of energy, such as mechanical or electrical energy. This transformation of energy is essential in understanding how heat plays a role not only in warming objects but also in driving different processes and systems.

On the Fahrenheit scale, the boiling point of water is 212°F. This scale was developed by Daniel Gabriel Fahrenheit and is commonly used in the United States for everyday temperature measurements.

A Clinical Thermometer is specifically designed to measure human body temperature, typically ranging from 96°F to 110°F (35°C to 43°C). These thermometers are essential tools in medical settings and households for monitoring body temperature.

The Celsius and Fahrenheit scales intersect at -40 degrees, where -40°C is equivalent to -40°F. This interesting temperature provides a direct conversion point between these two commonly used temperature scales.

Thermal expansion refers to the increase in size of a substance when it is heated. This fundamental concept is crucial in understanding how materials respond to changes in temperature, impacting various aspects of engineering, construction, and everyday applications.

Superficial expansion in solids specifically refers to the expansion in area when the material is heated. Understanding the different types of expansion in solids is essential for engineers and designers to account for dimensional changes in structures and components due to temperature variations.

The anomalous expansion of water is a unique property where water experiences a decrease in volume as it is heated up to 4°C before expanding again. This behavior is crucial for aquatic life as it causes water bodies to freeze from the top down, enabling life to survive beneath the icy surface. Understanding this anomaly is vital for various scientific and environmental applications.

The specific heat of water is 4200 J/kg°C, which means it takes 4200 Joules of energy to raise the temperature of 1 kilogram of water by 1 degree Celsius. This high specific heat of water makes it an excellent coolant in radiators and useful for processes like fermentation due to its ability to absorb and retain heat effectively.

The Second Law of Thermodynamics states that heat cannot transfer from a colder body to a hotter body spontaneously. This principle is crucial in understanding the direction of heat flow and is the basis for various aspects of energy conversion, including the operation of refrigerators.

Convection is the method of heat transfer that occurs in fluids like liquids and gases through the actual movement of particles. This process involves the transfer of heat through the circulation of the fluid, where warmer fluid rises and cooler fluid sinks, creating convection currents. Convection is essential in phenomena like sea and land breezes and plays a crucial role in various natural and artificial processes.

Kirchhoff's law dictates that the ratio of emissive power to absorptive power for any body remains constant and is equal to the emissive power of a black body. This fundamental principle underscores the consistent nature of how bodies emit and absorb radiation, highlighting a key aspect of thermal radiation behavior.

Stefan's Law elucidates that the energy radiated per second per unit area by a perfect black body is directly proportional to the fourth power of its absolute temperature. This signifies a significant relationship where the emission of energy intensifies rapidly with rising temperatures, showcasing the fundamental connection between temperature and energy radiation.

Wien's Displacement Law establishes an inverse relationship between the wavelength at which a black body's radiation emission peaks and the body's absolute temperature. This principle highlights how as the temperature increases, the peak emission wavelength shifts towards shorter, higher-energy wavelengths, illustrating a key aspect of thermal radiation behavior in black bodies.