Heat and Temp. PDF

Chapter 13 & 14 Why Crocodiles basks on the rock? LEARNING OBJECTIVE LECTURE 1 WHAT IS HEAT? WHAT IS THE TEMPERATURE? TYPES OF THERMOMETERS SOLVE SAMPLE PROBLEMS INVOLVING TEMPERATURE CONVERSION FORMULA LECTURE 2 DIFFERENCES BETWEEN CONDUCTION, CONVECTION A...

Chapter 13 & 14 Why Crocodiles basks on the rock? LEARNING OBJECTIVE LECTURE 1 WHAT IS HEAT? WHAT IS THE TEMPERATURE? TYPES OF THERMOMETERS SOLVE SAMPLE PROBLEMS INVOLVING TEMPERATURE CONVERSION FORMULA LECTURE 2 DIFFERENCES BETWEEN CONDUCTION, CONVECTION AND RADIATION? THERMAL CONDUCTORS AND INSULATORS THE CORE BODY TEMPERATURE HOW THE HEAT LOSS FROM OUR BODY? Lecture 1 LEARNING OBJECTIVE WHAT IS HEAT? WHAT IS THE TEMPERATURE? TYPES OF THERMOMETERS SOLVE SAMPLE PROBLEMS INVOLVING TEMPERATURE CONVERSION FORMULA  Heat vs Temperature Cup gets cooler while hand gets warmer Ice gets warmer while hand gets cooler Heat vs Temperature Temperature refers to the intensity of heat, measuring the average kinetic energy of molecules in a substance. Or It is a measure of the hotness or coldness of an object. Heat refers to the amount of energy in an object, measuring the total energy (kinetic and potential) contained by the molecules in that object. Heat is energy in transit between two objects or systems due to a temperature difference between them. Temperature is the measurable quantity of heat and heat can be derived from the temperature. Heat transfer from one body to other whereas the temperature cannot transfer. Heat flows spontaneously from a system at higher temperature to one at lower temperature. The temperature difference between two object cause the heat transfer. Unit Heat – J, Calories Temperature – K, oC, oF Thermal equilibrium A system is said to be in thermal equilibrium when there is no temperature difference between system and surroundings. Temperature Scales Celsius: The most used temperature scale in the world is the Celsius scale. On the Celsius scale, 0°C is the freezing temperature of water at P = 1 atm (the ice point) and 100°C is the boiling temperature of water at P = 1 atm (the steam point). Fahrenheit: At 1 atm, the ice point is 32°F and the steam point is 212°F, so the difference between the steam and ice points is 180°F. A temperature difference of 1°C is equivalent to a difference of 1.8°F TF = (1.8°F/°C)TC + 32°F Kelvin (SI Unit): 0 K represents absolute zero—there are no temperatures below 0 K. The ice point is 273.15 K TC = T − 273.15 Temperature Conversion Formulas Celsius to Fahrenheit -- TF = (1.8)TC + 32 Fahrenheit to Celsius -- TC =(TF – 32)/ 1.8 Celsius to Kelvin -- TK = TC + 273.15 Unit of Heat : Joule and calorie The calorie is defined as the heat required to change the temperature of 1 g of water by 1° C. Let's Do it !!! 1. A friend suffering from the flu feels like she has a fever; her body temperature is 38.6°C. What is her temperature in (a) K and (b) °F? 2. Convert the normal human body temperature (98.6°F) to degrees Celsius and kelvins. Temperature measurement devices in healthcare system Temperature monitoring is a fundamental aspect of healthcare, playing a crucial role in diagnosing and managing various medical conditions. Accurate and continuous temperature assessment is vital across multiple clinical settings, including hospitals, outpatient clinics, and home care. The common instrument for temperature measurement is the Thermometers.  Types of Thermometer There are various types of thermometers available.  Infrared Thermograms A device (camera) that measures the amount of radiant energy given off by an object It can tell the temperature of an object from a great distance away -hotter objects - yellows, reds and whites -colder objects - blues, purple, and black Can you spot the person in this picture who has the flu?  Homework -1 At what temperature is the Celsius temperature and the Fahrenheit temperature are same? A. 30oC B. 35oC C. -40oC D. 45oC E. -30oC Homework -2 o If the temperature changes by 36 F, then What is the change in Celsius? A. 30 oC B. 26 oC C. 36 oC D. 20 oC E. 0 oC Homework -3 If the temperature of a room is 62oF, then what is the temperature of the room in Kelvin? A. 289.8 K B. 291.7 K C. 300.0 K D. 307.8 K E. 312.0 K  Lecture 2 LEARNING OBJECTIVE DIFFERENCES BETWEEN CONDUCTION, CONVECTION AND RADIATION? THERMAL CONDUCTORS AND INSULATORS THE CORE BODY TEMPERATURE HOW THE HEAT LOSS FROM OUR BODY?  Heat always transfer from a hot object to a cold object. Heat Transfer Heat transfer in the following methods Conduction Convection Radiation Thermal Conduction Conduction is the process by which heat energy is transmitted through collisions between neighboring atoms or molecules. It can take place within solids, liquids, and gases. Conduction is due to collisions between atoms (or molecules) in which energy is exchanged. Heat flows from the higher-temperature region to the lower-temperature region. The atoms that are vibrating in the object at higher temperature collide with atoms in the object at lower temperature, resulting in a net transfer of energy to the colder object. Conduction is the main way for heat to transfer in solid. Thermal Conduction The total heat transferred depend on: 1. The area of contact 2. The temperature difference 3. The time of contact 4. The thermal conductivity of the materials Δ𝑇 The rate of heat flow (or power), 𝒫 = Q/Δt is 𝑃 = 𝐾𝐴 𝑑 where κ is the thermal conductivity of the material, A is the cross-sectional area, d is the thickness (or length) of the material, and ΔT is the temperature difference between one side and the other. All solid materials conduct heat, but some do a better job than others. Generally, metals are good conductors while porous materials are not. Good conductors of electricity are usually good conductors of heat. Thermal conductors and lnsuators Thermal conductors are substances that rapidly transfer heat. Thermal lnsulators are substances that slowly transfer heat. Thermal Convection Convection is the movement of particles through a substance, transporting their heat energy from hotter areas to cooler areas. Convection occurs when heat flows by the mass movement of molecules from one place to another. Convection can occur only in fluids, not in solids. Air is a poor conductor of heat, but it can easily flow and carry heat by convection. Convection may be natural or forced. Thermal Convection Convection occurs when heat flows by the mass movement of molecules from one place to another. It may be natural or forced. Thermal Convection The air circulation which is established by a room radiator. The air near the radiator is heated by conduction making it less dense than the cooler air in the room. Therefore, the warmer air rises and is replaced by the cooler air down- wards around the radiator. Thermal Convection Natural and Forced Convection In natural convection , the currents are due to gravity. Fluid with a higher density sinks because the buoyant force is smaller than the weight; less dense fluid rises because the buoyant force exceeds the weight. In forced convection, fluid is pushed around by mechanical means such as a fan or pump.  Application: Forced Convection in the Human Body The heart pumps blood around the body. When our body temperature is too high, the blood vessels near the skin dilate so that more blood can be pushed into them by the heart. The blood carries heat from the interior of the body to the skin; heat then flows from the skin into the cooler surroundings. If the surroundings are hotter than the skin, such as in a hot tub, this strategy backfires and can lead to dangerous overheating of the body. The hot water delivers heat to the dilated blood vessels; the blood carries the heat back to the central core of the body, raising the core temperature. Thermal Radiation Radiation is the transfer of energy that comes from a source and travels through space in the form of an electromagnetic radiation. All objects emit energy through electromagnetic radiation depending on the temperature of the object. Unlike conduction and convection, radiation does not require a material medium. An object emits thermal radiation while absorbing some of the thermal radiation emitted by other objects. Application: Radiation Thermography - the detailed measurement of radiation from the b o d y c a n be used in medical imaging. Warmer areas may be a sign of tumors or infection; cooler areas on the skin may be a sign of poor circulation.  What is core body temperature? The vital organs located deep within the body, such as the heart, liver and kidneys, are maintained at 37°C. This is the core body temperature. Skin temperature at the body's extremities, such as the fingers and toes, is usually lower than the core body temperature. On a warm day, skin temperature may be just 1 °C lower than the core body temperature, but on a very cold day it could be up to 9 °C lower. Finding the right balance Core temperature is maintained by balancing heat gain and heat loss. How can heat be gained? ✓ movement and exercise ✓ shivering ✓ vasoconstriction How can heat be lost? ✓ sweating ✓ vasodilation  Homeotherms and Poikilotherms Why Crocodiles basks on the rock?