Question

write the definition and the formula for each statment

9. HEAT:

heat and laws of thermodynamics;? methods for temperature measurement;? internal energy;?

effects of heat;?

energy requirement of people;? thermoregulation;?

heat transfer;?

convection;?

radiation;?

evaporation;?

heat application in medicine ?

Answer 1

Heat

Heat specifies to the state of energy an substance has in connection to the kinetic energy of its molecules or atoms. For instance if we consider an ice shelf likewise has enormous measure of heat energy as it has countless amount of molecules. Heat transfer from warmer substance to cooler substance which means it goes down a temperature gradient. Therefore heat is considered in usual energy units as Joule (J). As heat is considered as energy the heat also possess conservation which means an object does not possess heat, its temperature increased because the energy gained from the higher temperature object.

Laws of Thermodynamics

Two thermodynamic systems are each in thermal equilibrium with a third one, then they are in thermal equilibrium with each other and it states the Zeroth law of thermodynamics.

First law of thermodynamics conveys the conservative nature of heat. The energy can neither be created nor be destroyed. It can be transferred from one system to other.

Second law of thermodynamics states that it is impossible to use all the heat of one substance completely as work because some amount of heat is transferred to the surrounding or cold reservoirs. The second law of thermodynamics also says that the entropy of any isolated system dependably increments. Separated systems unexpectedly develop towards thermal equilibrium.

The third law of thermodynamics expresses that the entropy of a system approaches a constant value as the temperature approaches absolute zero.

Measuring temperature

There are four types of methods to measure temperature which follows different principles to measure

1. Mechanical devices such as liquid in glass thermometer, bimetallic strips etc, (Principle: Some substances are sensitive to the temperature which under goes mechanical motion like materials expands with raise in temperature)

2. Thermocouple which is consist of two dissimilar metals, joined together to form a junction where it forms a voltage. And this voltage is proportional to the temperature difference between the junction of the metals. (Principles such as Peltier effec, Seebeck effect, Thompson effect)

3. Thermoresistives or thermistors or RTD (resistance temperature detectors) which follows the principle if there is a change in temperature causes the electrical resistance. The electrical resistance caused is assumed to be temperature change.

Internal Energy

An object does not have 'heat'; it has internal energy that can be expanded by exchanging energy from a higher temperature object, for example heating.

Effects of Heat

Heat is a form of energy when is supplied to a object its temperature increases. When there is increase in temperature some substances possess mechanical changes, some possess chemical changes and physical changes (pressure, temperature, volume). Sometimes the heat energy limit exceeds there is a chances of catching fire. Heat is a form of energy which can be supplied to a system and use it as mechanical work such as mechanical engine.

Convection

Convection refers to the movement of molecules away from a warm object as a consequence of their reduced density as they gain heat and expand. This creates convection currents, which transfer heat away from the object.

Radiation

Heat can likewise be exchanged without the nearness of a medium. This happens by the procedure of radiation. Thermal radiation is a type of electromagnetic radiation like light. It goes in straight lines, can be reflected, and its intensity complies with the inverse square law.

Evaporation

Evaporation alludes to latent heat losses, for example at the point when a liquid believers to a gas, it needs to gain energy to do as such and this energy as heat is taken from the patient.

Medical applications of heat

These physical principles are significant in that heat in patients, and along these lines their temperature, has a course on their soporific administration and their postoperative recuperation. A few examinations have appeared hypothermic patients (for example center temperature <36°C) have possibly serious physiological unsettling influences. A temperature of 36°C is the standard being utilized by the National Institute of Clinical Excellence direction, beneath which is named unintentional perioperative hypothermia. Patients experiencing anesthesia have their physical and conduct reactions to cold canceled.