KERALA PSC / PHYSICS / HEAT AND THERMODYNAMICS / OBJECTIVE QUESTIONS / STUDY MATERIALS / GENERAL KNOWLEDGE / KERALA PSC PRELIMINARY / NOTES

 

KERALA PSC / PHYSICS / HEAT AND THERMODYNAMICS / OBJECTIVE QUESTIONS / STUDY MATERIALS / GENERAL KNOWLEDGE / KERALA PSC PRELIMINARY / NOTES

KERALA PSC / PHYSICS / HEAT AND THERMODYNAMICS / OBJECTIVE QUESTIONS / STUDY MATERIALS / GENERAL KNOWLEDGE / KERALA PSC PRELIMINARY / NOTES

·      Heat is a form of energy arising from mechanical motion of the molecule, all things are made up of atoms and molecules which are always moving. The motion gives every object’s internal energy.

·      Temperature is an indication of an object’s internal energy

·      Thermodynamics is the study of relationship between heat and other form of energy, it is based on three laws.

Scale of temperature: Commonly used temperature scales are Celsius scale Farenheit scale, Remur Scale and Kelvin scale or Absolute scale. The relationship between first three temperature scale is C /5 = F – 32 / 9 = R / 4

C – Celsius, F – Farenheit, R – Remur Scale

Absolute or Kelvin Scale: Absolute zero in which temperature is -273⁰C. The molecule have the lowest possible kinetic energy.

Since -273C = 0 K

Then 0⁰C = 273 K

100⁰C = 273 + 100 = 373K

·      Absolute zero is the lowest possible temperature which is equal to 0K or -273.16⁰C or -459.69⁰F.

·      Temperature is the degree of hotness and heat is a form of energy which increases the temperature of a body

·      Specific heat capacity of a substance is the amount of heat required to raise the temperature of the substance through 1⁰C.

·      As we go up in the atmosphere, the temperature decreases

·      Plasma is the fourth state of matter. Solid, liquid and gas are other three states of matter.

·      First law of thermodynamics state that, if heat is supplied to a system capable of doing work, then the quantity of heat energy absorbed by the system will be equal to the sun of the increase in internal energy of the system and the external work done by it.

·      A black surface absorbs heat more than other colours

·      Cryogenics is concerned with the production, control and application of extremely low temperature.

·      At ultra-high temperature matter exist in plasma form 99% of matter in the Universe in plasma form.

·      One Calorie is the amount of heat needed to raise the temperature of 1 gm of water by 1⁰C.

·      Steam causes more severe burns than water of the same temperature because steam possess more heat energy due to latent heat than water.

·      Transmission of heat from one point to another without heating the medium is called radiation.

·      Cotton dresses are safe for wearing while cooking

·      Conduction is the process of net energy transfer through a substance without the movement of the substance itself, but by molecular collisions

·      Ebonite and asbestor are the worst conductor of heat and are called insulators, example of good conductor is silver, copper, mercury etc…

·      Air is one of the worst conductor, this keeps house warmer in winter and cooler in summer

·      Convection: Convection is the flow of heat through or fluid from place of higher to place of lower temperature by movement of fluid itself, convection occurs in liquid as well as in gases.

·      Radiation: Radiation is the flow of heat from one place to another by means of electromagnetic waves. In conduction and convection motion of particle transmit heat but in radiation heat can travel through vacuum energy from the sun travels through space to earth by means of radiation.

·      Very poor conductor, such as glass are called insulators. Air is a good insulator.

·      Mica is a good conductor of heat, but a bad conductor of electricity

·      Black surface is a good radiator as well as a good absorber of heat

·      White clothes are preferred in summer, as these absorb less heat from the surroundings

·      Solar cooker uses the green-house effect

·      Transference of heat takes place in liquids and gases mostly by convection.

·      Perspiration is maximum, when temperature is high and air is humid

·      Evaporation takes place at all temperatures and is accompanied by cooling

·      Melting point of ice can be raised by the decrease of pressure.

·      Water has maximum density at 4⁰C. Water expands when it freezes. Water occupies maximum volume at 0⁰C.

Unusual Behaviour of water at 4⁰C

·      When water is cooled to 4⁰C it contracts as we would expect, but as it cools from 4⁰C to 0⁰C it began to expand surprisingly water therefore has maximum density at 4⁰C, further cooling of ice causes it to contract.

·      The behavior of water between 4⁰C and 0⁰C explains why fish survive in frozen pond.

·      Specific latent heat of fusion: The specific latent heat of fusion of substance is the amount of heat required to change 1 kg from solid to liquid without temperature change, for 1 kg of ice it is 334000 J Kg.

·      Specific latent heat of Vaporization: The specific latent heat of vapourization of a substance is the amount of heat required to change 1 kg from liquid to vapour without temperature change for water it is 2,260,000 J/Kg. This is why burn from steam may be more serious than the boiling water.

·      Heat engine is a device which changes heat energy obtained by burning a fuel to kinetic energy. Eg: internal combustion engine used in vehicles.

·      Steam turbines are used in power stations and on ships

·      The Clinical Thermometer is specially designed to measure human body temperature. Normal human body temperature is 36.9⁰C (or 98.4⁰F)

·      Melting point of mercury is -39⁰C and that of alcohol is -115⁰C.

·      The main source of energy in the biosphere is solar energy which reach earth by means of radiation.

·      Water expands on freezing. Due to this reason when water is filled in a bottle and is allowed to freeze the bottle breaks, and during winter water pipes break in cold regions.

 

KERALA PSC / PHYSICS / HEAT AND THERMODYNAMICS / OBJECTIVE QUESTIONS / STUDY MATERIALS / GENERAL KNOWLEDGE / KERALA PSC PRELIMINARY / NOTES