Engineering

In this article we will discuss different facts related to Low Limit Switch. As the name indicates Low Limit Switch is used for control applications.

Low Limit Switch is most widely used in the equipments where low temperature protection is a prior requirement. Low Limit Switch(also known as Freeze Stats)is designed with a vapour charged capillary sensing tube.

 

Mainly used in refrigerated cells and different equipments where operational temperature is maintained very low, minimum operational temperature is up to -40°C.

What is Low Limit Switch?

The Low Limit Switch plays the role of frost protection switch in water treatment and water supply plants, HVAC air conditioning( preferred in cold areas) etc.

Low Limit Switch is designed to monitor low temperature and to prevent damages that may occur due to frost accumulation. Generally suitable for hot water coil pipe unit, cold water pipe unit, heat exchanger, liquid carrying pipelines, surface air cooler etc.

Certain features of Low Limit Switch which make it more versatile for its wide range of application are easy to read dial, compact size, high reliability, quick response action etc.

Low Limit Switch Working Principle

The working principle of Low Limit Switch is single- pole double-throw.

Low Limit Switch consists of a long copper capillary tube, full of vapour inside and acts as a sensing part. If any part of the capillary has senses a temperature lower than the setup point, inner switch will be off until temperature rises upto 2 or 2.5 °C than the set temperature. After that again the switch starts working.

To detect the low temperature and protective action the capillary tube is enclosed inside the pipeline. The long sensing tube contains vapour and the main body has an adjustable enclosure.

Generally freeze stats are made of 1/8”OD flexible tubing, filled with temperature sensitive gas vapour, the pressure of gas vapour goes down with decreasing temperature. The capillary tube is connected to a control box, where a temperature is set(35 F typically).

If any part of the temperature sensor element experiences a temperature drop lower than the predetermined or set point, the freeze stat will immediately trip. The sensor element has different lengths up to of 20 ft long and generally trip occur if the length within 12” to 18” goes lower than the set point.

Low Limit Switch were designed for use on HVAC equipment which require low temperature cut out protection to prevent cooling coils from freezing. Low Limit Switch is connected between the heating and cooling coils on the supply side of the fan unit and gives an indication of lower temperature as per the senses received by the sensing element.

Low Limit Switch or Freeze Stats has both automatic and manual reset versions with a wide range of capillary lengths.

Applications of Low Limit Switch

Low Limit Switch protects cooling coils in air handler systems by preventing frost build up.

Low Limit Switch are most widely used in HVAC equipments, cooling coils and heat exchangers.

 The thermostat and capillary sensing element provide an antifreeze function by sensing the lowest temperature along any one foot section of capillary tube. Automatic reset relays signal the building management system and also cut off the fan. As the temperature goes below the fixed safety point(set point), the low limit Switch immediately detects it.

Low Voltage Limit Switch

Low Voltage Limit Switch is used to control loads such as blower fans and heating elements without an intervening relay.

Low Voltage Switch is connected in circuits where a low voltage has to be maintained for perfect running of the machine. In case of a magnetic relay circuit it is so connected that a drop in voltage cause the motor starter to disconnect the motor from the line.

Limit Switches are used in a wide range of application including the production floor as well as daily lives. Limit Switches are the mechanical/electronic components on a production floor for control and safety purposes. Although the function of a Limit Switch is very obvious, wide variety of these switches are available in the market to offer flexibility.

Low Temperature Limit Switch

Low Temperature Limit Switch is a special version of limit switches designing for low operational  temperature applications  such as refrigerated cells or equipments.

Temperature Limit Switch controls the electrical circuit which in turn regulates the machine and its moving parts as per the requirement. Special materials are used to manufacture Low Temperature Limit Switches and it can perform well at an operational temperature below down to -40°C.

Low Temperature Limit Switch acts as a pilot device in magnetic starter control circuits and allow it to regulate the start, stop, slow down or accelerate the functions of an electric motor.

Some of the manufacturer design certain Low Limit Switches that can be used in the most hazardous and arduous application of industries to withstand harshet conditions and duty cycles including extreme cold at -60 °C.

How to Test a Low Limit Switch?

With the help of a basic Ohmmeter or Digital Multi-meter we can know whether the Limit Switch is working or not.

To test a Limit Switch we have to follow the following steps:

1. first disconnect the switch from the system and then place the Digital Muliti-meter leads to each terminal.
2. The resistance should be very high for a normally open(NO)limit switch.
3. If the Limit Switch is normally closed(NC), the resistance should be closed to zero.
4. Now keeping the limit switch into active position, measure the resistance.
5. It should be the opposite in this setting, if there is no transition, the limit switch is bad.

Installation of a Low Limit Switch

The steps followed for installation of a Low Limit Switch are as follows:

• To install on a wall, make a hole with the help of a drilling machine as per the instructions in the manual and then lock the switch using self-tapping screw.
• Set the temperature in such a manner that environmental temperature should not be less than the setting temperature. Environmental temperature shouldn’t be lower than setting temperature.  Keep away from cold and hot sources and avoid installing in outdoor.
•  Never press the sensing capillary to avoid change in calibration result to maintain accuracy.
• For ensure accurate and reliable action, should at least wrap over 200mm length sensing capillary onto pipeline of related protection devices.
• In case of heat exchanger and surface air cooler, the sensing capillary of the limit switch should be installed at their leeward side.
• Make sure that power should be OFF before staring wiring to avoid any kind of accident.

In this article we will discuss about Radioactive Waste Examples which are quite hazardous.Radioactive waste are the by product from different activities  like nuclear research, nuclear power plants, defence sectors, earth mining, hospitals etc.

Examples of Radioactive waste are listed below:

• Wastes from Defence Activities
• Mill Tailings
• Transuranic waste
• Electricity Generation
• Nuclear fuel cycle
• Reprocessing of used fuel
• Mining through to fuel fabrication
• Decommissioning and dismantling of nuclear reactors
• Waste from Nuclear Conflicts
• Natural nuclear waste sources
• Waste from Medical purposes

Radioactive waste mainly contains radioactive materials due to which the disposable and storage of these waste is an important matter of concern.

Production of radioactive waste should be avoided as much as possible. If the production of radioactive waste is unavoidable, then try to minimise the production rate.

What is a Radioactive Waste?

Radioactive waste should be always managed with care and following the restrictions as per the Government rules throughout its life cycle starting from arising to recognised end point.

Once the radioactive waste has been generated, its influence does not end until it is decayed naturally. Packaging of radioactive waste in containers doesn’t reduce their radioactivity and radioactivity reduction by dilution is an expensive option.

Most of the industries produce radioactive waste in large amount and these wastes should be disposed safely to avoid the spread of contamination. 

Radioactive Waste Examples in Details

Radioactive waste is considered as a serious threat to mankind as well as nature because of its long duration for decantation.

Wastes from Defence Activities

Radioactive waste produced from defence activities are similar to wastes produced from nuclear power plants, but the amount of waste produced is much less if we compare it with total amount of waste production. The sources of production are activities like Navy operations, decommissioning of nuclear powered submarines, clean up of disused military sites etc.

Mill Tailings

They are the by product during the milling process of certain ores to get uranium or thorium. Mill Tailings  consist of thorium, radium and small residual amount of uranium. Mill tailings are not highly radioactive due to the less amount of radioactive materilas but possess long half lives.

Transuranic waste

These type of waste are contaminated with alpha-emitting transuranic  radionuclides and have a half lives more than 20 years, but they are not classified as HLW. More caution is required for its disposable  than LLW and ILW due to the longer half live. Transuranic waste, sometimes called TRU are obtained generally from the manufacturing process of nuclear weapons.

Electricity Generation

Use of nuclear reactors to generate electricity is a major source of radioactive waste, which can be classified as HLW. The reactor operation results highly reactive fission products, uranium and plutonium produce transuranic elements which mix with used fuel.

Nuclear fuel cycle

The whole cycle of nuclear fuel starting from radioactive fuel extraction, processing, uses and finally disposal generate radioactive wastes. If the disposal process is not proper enough then the rate of waste production is quite high.

Reprocessing of used fuel

Used fuel also possess radioactivity because they still contain some amount of U-235,different plutonium isotopes, U-238, the amount can be resemble with 96% of original uranium content and almost half of the original energy content. These used nuclear fuel has been reprocessed to extract fissile materials and also to reduce the volume of HLW.

Mining through to fuel fabrication

Fine sandy tailings are generated from the uranium mining operation and these tailings contain all the radioactive elements which are available in uranium ore.  Generally tailings are kept under water in dams and after few months covered with a layer of clay and rock to prevent the leakage of radon gas.

Decommissioning and dismantling of nuclear reactors

Decommissioning and dismantling of nuclear reactorsand other nuclear facilities are also responsible for radioactive waste generation.

Waste from Nuclear Conflicts

Nuclear conflicts among different countries is a source of radioactive wastes on a large scale. In this case, due to the use of nuclear arms a vast area may be contaminated by radioactive materials and the effect of contamination in the soil remains for a quite long period of time which is really hazardous for human being, animal and for the whole atmosphere.

Natural nuclear waste sources

Crude oil, natural gas, coal etc are nuclear materials available in our nature. These radioactive materials generate radioactive waste during the industrial processes to extract them for commercial purposes. Coal power plants, oil refineries and drilling plants, gas industries produce radioactive by products like radium, radon etc.

Waste from Medical purposes

Medical  is one of the main sources of radioactive wastes, medical research for medicines and different medication facilities generate huge amount of radioactive wastes. For example, during  the surgery of  thyroid cancer, lymphoma, bone cancer etc radioactive wastes are produced. 

Classification of Radioactive Waste

Radioactive wastes are classified depending on the amount of radioactivity present and the heat produced by this radioactivity.

Radioactive waste are classified as below:

• High Level Waste (HLW): Majority of radioactivity is associated with HLW, temperature may rise significantly due to their radioactivity, the storage and disposal of these wastes should be well planned. When the production of electricity has been completed, a huge amount of HLW is remaining in the form of  spent fuel inside the reactors. These are highly radioactive and emits heat, HLW always require cooling and shielding for disposal.  
• Low Level Waste(LLW):Generally produced from reactor operations, medical, academic, factories and other commercial activities where radioactive materials are used. LLW are contaminated with radioactive materials and sometimes become radioactive through exposure to neutron radiation. Some LLW are wiping rags, mops, tools, papers, filters, clothing, medical tubes, injection needles which have small amount of short lived radioactivity. LLW may be stored on site by licensees until has been decayed away or disposed as common trash.
• Intermediate Level Waste(ILW):They contain higher amount of radioactivity and need some shielding, more radioactive than LLW. But heat generation is less than 2 KW/m³, so design or selection for storage and disposal is not considered much. Contaminated materials from reactor decommissioning, chemical sludge, resins, metal fuel cladding etc typically considered as ILW.

• Very Low Level Waste(VLLW):Amount of radioactive materials present in VLLW is not considered as harmful to people or surrounding environment. Examples of VLLW are demolished materials like concrete, plaster, bricks, metal rods, pipes, valves etc obtained during dismantling works on nuclear industrial sites. Food Processing, chemical, steel industries also produce VLLW, as small amount of radioactivity present in certain minerals used in their manufacturing processes.

Effects of Radioactive Waste

Major effects of Nuclear Waste are as follows:

• Though great care is maintained for the transportation of radioactive waste, sometimes leakage or accident may occur. The leakage of radioactive waste during transportation will lead to soil contamination and make it unusable for cultivation, the effect remains for a long period of time because many of them have a long half lives. 
• Radioactive waste can cause serious diseases for human being as well as animals which may lead to even death. In a long term it can change the DNA structure and alter the future generations.
• The area which is used for storage purpose is fully polluted and becomes useless for any other activities.
• Radioactive waste has a significant adverse effect on nature.
• A significant effect can be observed in nature including plants and animals which in turn influence the human life through the food chain.

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In this article “Ionization energy examples” with their detailed explanations are derived. The meaning of higher ionization energy means facing the difficulty to subtract any electron from the chemical bonds.

11 + ionization energy examples are listed below,

• Fluorescent lamp
• Electrical bulbs
• Solvation
• Calcium nitride
• Free radicals
• Condensation reactions
• Sodium chloride
• Hydrogen
• Nitrogen
• Oxygen
• Aluminium

Fluorescent lamp:

Fluorescent lamp is a very light weight vapor lamp which inside mercury is present. In the fluorescent lamp fluoresce is placed for this reason visible light is delivered.  Fluorescent lamp works in electric current. When electric current is deliver to the fluorescent lamp that time gas is energized the vapor of mercury from this ultraviolet radiation is emitted and the radiation of ultraviolet objective the coating of the phosphor in the liner wall of the lamp.

Fluorescent lamp main parts:–

• Electrodes
• Starter
• Tube
• Gas
• Phosphor coating
• Ballast

Electrodes:-

Inside the fluorescent lights two set electrodes are situated. The electrodes in fluorescent lights are attached with the fixture through two small size metal prongs. These prongs are clearly visible to the outside of the fluorescent lights. In the CFLs electrodes are not visible from the outer side because its base is screw type.

Starter:-

Only in the older type fluorescent lights have the component name starter. These starters are small metal cylinder. The starters of the fluorescent lights cause the delay of the electricity to the gas tube.

Tube:-

In the tube of the fluorescent light gas is placed. The usual fluorescent lights are tube shaped into the straight cylinder. In the CFLs, compact fluorescent light have a tube which is bending and look like U letter. In neon lights tubes are looks like words or graphics.

Gas:-

In the fluorescent light tube some gases are inset such as argon, xenon, neon and also vapor of mercury is placed. Gas of the fluorescent light is help to discharging the light. When a particular amount of voltage is applied the atoms of the ionized gas is charged and excited. At this moment proton of the ionized gas atoms also excited.

Phosphor coating:-

With the help of a metal named phosphor the inside tube of fluorescent light is coated. The coatings of the phosphor affect the colour emitting of the fluorescent light.

Ballast:-

In the fluorescent light the ballast can be two types one is electronic and another one is magnetic. In the new type of fluorescent light only the electronic ballast is present it is not too loud or hot like magnetic ballast.

Advantages of fluorescent lamp:-

• Low heat radiation
• Lower power consumption
• Longer life
• Not required warning up period
• Good quality of light
• Higher efficiency

Disadvantages of fluorescent lamp:-

• Initial cost is high
• Fluctuation of voltage is affected
• Produce radio interface
• Sometime light output is fluctuating

Electrical bulbs:

Electrical bulb is actually a simplest version of an electrical lamp. The electrical bulb is actually a very small size and simple light source which helps to brighten the dark place. The other name of the electrical bulb is incandescent bulb.

Application of Electrical bulb:-

• In portable lighting the electrical bulb is widely used such as table lamps
• In vehicle headlights and lights the electrical bulb is used
• Commercial lighting
• Household lighting
• Advertising and decoration the electrical bulb is used.

Advantages of Electrical blub:-

• No harassment in installation
• Longer life period
• Economical
• Affordable
• Easily available in verities shapes and sizes
• Working period is also high
• High output

Disadvantages of Electrical blub:-

• Energy insufficient
• Produce warm light
• Need to handle very carefully because it is made of glass thus can brake easily
• Breakable parts are very sharp can cut in the skin
• Inside the electrical bulb mercury, argon is present for this reason the electrical bulb should be handle carefully.

Solvation:

Materials which are made of plastic they are attacked by chemical reaction and salvation. The process method of salvation only happened with polar solvents. The concept of salvation is distinct from solubility and dissolution.

Solvation can be explain as, the method in which chemical association is present between the solvent and molecules of solute.

The factors which are affecting solubility,

• Pressure
• Temperature
• Surface area
• ph
• Nature of Solvent/Solute

Read more about Pressure vessel : It’s important facts and 10+ applications

Calcium nitride:

The formula of the calcium nitride is Ca₃N₂. The molar mass of the calcium nitride is 148.25 gram per mol. The calcium nitride can present in a lots of state.

Free radicals:

A definition of free radical is any molecular house is capable to contain electron in unpaired state independently. Radicals can be present in two state one is unstable and another is highly reactive.

The radical can give an electron to other molecules or can take electron from other molecules. When the radical can give an electron to other molecules that time it behave like oxidants and when the radical can take an electron from other molecules that time it behave like reluctant.

Some sources name of the free radicals is listed below,

• Exercise
• Smoking
• Mitochondria
• Inflammation
• Phagocytosis
• Ozone
• Radiation
• Pesticides
• Pollutions of the environments
• Industrial solvents
• Xanthine oxidase

Condensation reactions:

The condensation reactions are a part of chemical reactions. In condensation reactions smaller size molecules join together and make a larger size molecule. In the condensation reactions monomers means the smaller size molecules made a bond and name colavent bond and this bond is allow the joining the molecules and to make larger molecules.

The examples of condensation reactions are Glucose, Galactose.

The formula of condensation reactions is,

AH + BOH ­-> AB +H₂O

Where,

A = The molecules in condensation reactions is condensed

B = The molecules in condensation reactions is condensed

AB = Compound product in condensation reactions

Sodium chloride:

The regular salt chemical name is sodium chloride. Sodium chloride is an electrolyte and helps to regulate the total quantity of water in our human body. But this chemical element also causes lot of problem in human body. They are listed below,

• Diseases of liver
• Diseases of kidney
• Congestive heart failure
• High blood pressure
• Fluid retention

Sodium Chloride preparation process:

When chloride and sodium mixed together then it is response to generate sodium chloride.

The formula in below,

2 Na (s) + Cl₂ -> 2NaCl (s)

Hydrogen:

The hydrogen is a family member of chemical elements. It is a tasteless, colourless, odourless, flammable gaseous matter. The atom of the hydrogen contain a nucleus which surrounding have proton bearing which have the charge of positive electrical charge and an electron bearing is present which have the charge of negative electrical charge. In the whole universe hydrogen is one of the most abundant matters.

Three isotopes are present in the hydrogen. The isotope mass 1 is called protium and it symbol is H, and written as H¹,  The isotope mass 2 is called deuterium and a nucleus is present which contain one proton one neutron and it symbol is d, and written as H², The isotope mass 3 is called tritium and it symbol is t, and written as H³ and its nucleus has one proton two neutrons.

Nitrogen:

In the periodic table of group 15 nitrogen is belonging. Nitrogen is lightest and non-metal of periodic table. In earth nitrogen is very important element. In the components of the nitrogen all proteins are placed. Nitrogen found in the system of living.

The atomic number of nitrogen is 7, atomic symbol is N. Most commons isotopes of nitrogen are Nitrogen – 14.

Applications of nitrogen:-

• Food packaging
• Manufacturing
• Aircraft fuel system
• Industry of light bulbs
• Fire suppression system
• Industry of chemical
• Tire filling system
• Manufacturing of electronics
• Manufacturing of stainless steel
• Fertilizer

Oxygen:

Pure form of oxygen is not flammable. It is a tasteless, colourless, odourless gaseous matter. In our surrounding some objects are present which are not burning in the air but can burn with the help of oxygen. Oxygen is very essential for our human life. The atomic number of oxygen is 8, atomic symbol is O.

It is reactive element and when it is added with another element oxide form. Oxygen could not make some oxide with some elements such as neon, argon, helium, and krypton.

Applications of oxygen:-

• Mining
• Rocket propulsion
• Production in glass industry
• Production in stone industry
• Medical field
• Biological field
• For melting and cutting of the metals

Aluminium:

In the table of the periodic aluminium is 13^th element means the atomic number of the aluminium is 13. Aluminium is higher reactive and it is always ready to combine with other elements, for this reason in environment aluminium not present itself it presence can be observe with other elements.

Aluminium has high electrical conductivity for this reason it is used in the cables of the electric. Aluminium is silver metal which have extremely high corrosion resistant compare to others metals.

Application of aluminium:-

• Personal vehicle
• Construction of ships
• As a components in aircraft
• Window frames
• Power lines
• Household
• Industrial applications
• Construction of trains
• High rising building

Frequent Asked Questions:-

Question: Ionization energy examples based on which equation?

Solution: The basic ionization energy equation is,

X(g) -> X (g) + e

More ionization energy equations,

1^st equation of the ionization energy is,

X(g)  -> X +  (g) + e^-

2^nd equation of the ionization energy is,

X(g)  -> X2 + (g) + e^-

3^rd equation of the ionization energy is,

X2(g)  -> X3 + (g) + e^-

This article discusses about thermal radiation example. Radiation is nothing but a mode of heat transfer which does not need any medium for the transfer to take place.

It is notable fact that for radiation heat transfer to take place, even physical contact is not required. The heat gets transferred without any medium in between or physical contact between the two systems. We shall discuss more about different examples of radiation heat transfer.

• Heat transfer taking place inside microwave oven
• Earth getting heated by Sun
• Heat being emitted by a radiator
• Light being emitted by an incandescent lamp
• Gamma ray emission from a nucleus
• Feeling warm when standing beside a car whose engine is hot
• Heat coming out of hot food
• Metal rod when heated emits heat to surroundings
• Molten metal used in casting emits heat in the surroundings
• Magma emits heat to its surrounding areas
• Standing beside a fire makes us feel warm
• Bike’s silencer emits heat when the bike is being driven or has just been driven
• We feel warm when standing beside a stove
• Laptop’s body emits heat when it is used for long hours
• Hot metal emits heat after being machined

What is heat transfer?

Heat transfer is the process in which thermal energy and entropy is transferred from one system to another.

Major factor which affects the heat transfer is the temperature difference between the two systems. The heat will flow always in the direction from high temperature to low temperature system. Although there are multiple modes of heat transfer but we shall limit our discussion to only radiation heat transfer.

Image credits: Kmecfiunit, cmglee, Heat-transmittance-means2, CC BY-SA 4.0

What is radiation heat transfer?

In simple words, radiation heat transfer is the type of heat transfer in which the system at lower temperature absorbs, reflects or transmits the heat that is being emitted by system at higher temperature.

It is a notable fact that radiation heat transfer does not need any medium or physical contact. The best example of radiation heat transfer is Earth getting heated by the heat being emitted by sun. This transfer of heat takes place through radiation heat transfer. We shall study more examples of radiation heat transfer in the later sections of this article.

Example of radiation heat transfer

Radiation heat transfer takes place around us but we usually ignore it. If we look around, there are many examples where we can see radiation heat transfer taking place.

Let us see some common examples of radiation heat transfer. They are given below-

Heat transfer taking place inside microwave oven

Microwave oven is used to heat food. The microwave oven sends out electromagnetic waves which penetrate the food and makes it warm. This way the heat transfer takes place.

Earth getting heated by Sun

Sun sends out electromagnetic waves to the vacuum of space. These waves are collected by Earth as a result of which the planet gets heated up. This is the most common example of heat transfer done by radiation.

Heat being emitted by a radiator

A radiator in vehicle sends out heat to the surroundings. If we are standing near the radiator, we are bale to feel the heat due to radiation.

Light being emitted by an incandescent lamp

An incandescent lamp becomes hot after being lit for some while. This heat is transferred to the surroundings with the help of radiation heat transfer. If we are standing near this lamp, we will be able to feel the heat. This is due to Radiation heat transfer.

Gamma ray emission from a nucleus

Gamma rays are an example of electromagnetic waves. These waves don’t need any medium to travel hence we can say that these waves travel with the help of radiation. When gamma rays are emitted by nucleus, they travel with the help of radiation. Any object coming in its close vicinity may experience radiation effects.

Feeling warm when standing beside a car whose engine is hot

When a car is used for long period, the engine becomes hot due to its long operation duration. The engine surface is hot but we can feel the heat without even touching the engine itself. This happens as a result of radiation heat transfer from the surface of engine to its surroundings.

Heat coming out of hot food

We feel the heat from warm food without even touching it. The plate becomes hot due to conduction taking place. But when we feel the heat without touching the plate or food, it is because of radiation heat transfer.

Metal rod when heated emits heat to surroundings

When we heat a metal rod using an external heat source, the rod gets heated up by the process of conduction. This heated rod transfers the heat to surroundings using radiation heat transfer. We need not touch the rod in order to feel the heat, we can just put our hand near the rod and we will know the rod is warm or not.

Molten metal used in casting emits heat in the surroundings

For casting a product, metal is melted into liquid. This requires immense heat, this heat is then emitted back to the surroundings. This happens as a result of radiation heat transfer between molten metal and surroundings.

Magma emits heat to its surrounding areas

Similar to molten metals, magma is molten rock. These molten rocks emit heat to the surroundings with the help of radiation heat transfer.

Standing beside a fire makes us feel warm

Fire emits heat to the surroundings. Without touching fire also, one can get burns on his hands. We can say that fire emits heat by the process of radiation heat transfer.

Bike’s silencer emits heat when the bike is being driven or has just been driven

The silencer used in bikes become hot after a long ride. The silencer is so hot that our legs can feel the heat just by keeping them near the silencer. If we touch the silencer we are surely going to get burnt due to heat transfer by conduction. But when we feel hot without touching it, it is due to radiation heat transfer.

We feel warm when standing beside a stove

When we lit up a stove, the heat from the stove s transferred to the surroundings with the help of radiation heat transfer.

Laptop’s body emits heat when it is used for long hours

The electronics used in laptop get hot when the laptop is used for long hours. This heat is transferred to the surroundings with the help of radiation heat transfer.

Hot metal emits heat after being machined

A metal becomes hot after it gets machined. This heat is generated due to friction. This generated heat is emitted back to surroundings with the help of radiation heat transfer.

The “Internal energy of an ideal gas” is not depending upon the path of a system which is closed but the internal energy of an ideal gas depends on the initial state and final state of the system.

From the law of thermodynamics we get a crystal clear concept about the internal energy of an ideal gas. The internal energy of an ideal gas can be explain as, the total amount of energy is amalgamated with the motion that could be vibration motion, rotation motion or translation motion of the molecules or atoms of a matter in the system.

Read more about Carnot Cycle: Its Important Features along with 16 FAQ’s

What is internal energy of an ideal gas?

For an ideal gas the amount of internal energy for a system only depend upon temperature. But for the real gas the amount of internal energy for a system depend upon temperature, volume, pressure.

The internal energy of an ideal gas is a property of extensive and the amount of energy of a gaseous matter cannot determine directly. The internal energy of an ideal gas is in a system the molecules of a gaseous matter, the amount of internal energy transferring in the form of thermodynamic work and heat.

For an ideal gas the total amount of internal energy is directly proportional to the temperature and also the total number of the molecules of mole of a substance which is present in the gaseous state.

Read more about Thermal diffusivity : It’s all Important Facts and FAQs

So mathematically the internal energy of an ideal gas can be express as,

dU = nC_vdT…… eqn (1)

Or, U = C_vnT…………. eqn (2)

From the equation (1) term nC_vT  is used from the kinetic energy of an ideal gas.

Where,

U = The amount of internal energy of a gas

C_v = At constant volume the amount of heat capacity of a gaseous substance

n = The total number of moles of a gaseous substance

T = Temperature of the system

Internal energy of an ideal gas formula:

In the thermodynamics the change of total amount of internal energy which is expressed as ΔU can determine but for an ideal gas the amount of absolute internal energy can estimate.

Internal energy of an ideal gas formula is,

Where,

U = Internal energy of an ideal gas

c_v = Heat capacity of the specific isochoric

m = Mass of an ideal gas

T = Temperature

To calculate the amount Internal energy of an ideal gas at first we need imagine a gas substance is blockaded to a cylinder that time the volume of the ideal gas should be in constant state and the ideal gas should to cool down and reaches at absolute zero temperature.

In this particular state all particles of the ideal gas at rest position and there is no internal energy is present. The total amount of heat is expressed as Q is transferred at the constant state of volume until the ideal gas temperature is reaches to T. Now in this state the total amount of heat which is necessary for the internal energy is reaches at U.

Internal energy of an ideal gas derivation:

In a system of thermodynamic the amount of internal energy can be converted into potential energy or kinetic energy. For the system of the thermodynamics three types of energy such as internal energy, potential energy and kinetic energy can contained.

Derivation internal energy for an ideal gas:-

For an ideal gas substance the internal energy depend upon the kinetic energy and potential energy.

We know that,

M/m = N_a

K_avg = 1/2 3RT/N_a

K_avg = 3/2 kT because  k = R/N_a

How does the internal energy of an ideal gas differ from that of real gas?

The ideal gas explain as, the gaseous substance which are obeys the law of gases at any condition of temperature and pressure. The real gas explain as, the gaseous substance which are not obeys the law of gases.

The difference between the internal energy of an ideal gas and real gas is discuss below,

Parameters	Ideal gas	Real gas
Pressure	High	Low
Intermolecular attraction force	Not present	Present
Volume	No definite volume	Definite volume
Existence in environment	Not present and the ideal gas is hypothetical gas	Present
Elastic collision of molecules	Yes	No
Interaction with others gas	No	Yes
Law of gases	Obey	Does not obey
Velocity	Not present	Present
Mass	Not present	Present
Volume	Not present	Present

Specific internal energy of an ideal gas:

The specific internal energy of an ideal gas which is expressed as u explain as, the amount of internal energy of an ideal gas matter in per unit mass of the particular ideal gas matter.

Read more about Specific Enthalpy : Its important properties & amp; 8 FAQ’s

The formula of the specific internal energy of an ideal gas is,

u = U/m

Where,

u = Specific internal energy of an ideal gas in joule per kilogram

U = Internal energy of an ideal gas in joule

m = Mass of an ideal gas in kilogram

The S.I. unit of the specific internal energy of an ideal gas is joule per kilogram. The dimension of specific internal energy of an ideal gas is L²T^-2.

Change in internal energy of an ideal gas:

From the laws of kinetic energy it’s clearly shown that kinetic energy of a particle has a directly relation with temperature from that change in internal energy of an ideal gas directly connected.

Change in internal energy of an ideal gas only depends on the temperature it is not depend on the other physical parameters like volume, pressure. If initial temperature, final temperature is known for the system then change in internal energy of an ideal gas easy to determined.

Whether the system can follow any process like isentropic, isobaric or isochoric or any other method the change in internal energy of an ideal gas is irrelevant. In one word we can say change in internal energy of an ideal gas only ruled by the state of the gaseous matter not ruled by the process of the gaseous matter. If the temperature is differ in the system only for that case internal energy can be differ for an ideal gaseous substance. The change in internal energy of an ideal gas can be zero in the process of isothermal.

Read more about Isothermal process : It’s all important facts with 13 FAQs

By the process of the thermodynamic the clear relation between change in internal energy of an ideal gas and temperature easily can investigate of gaseous matter.  In the process of isochoric on the gas no workdone is happened. In the process of isochoric on the gas heat is input for this reason change in internal energy of an ideal gas is increases.

What is the change of internal energy?

In a system of thermodynamic the change in internal energy is derive in this way the sum of the internal energy changes for the gaseous matter is equal to  the net workdone of a thermodynamic system and the total amount of heat is deposal to the system and the surrounding of the system.

The formula for the change in internal energy of an ideal gas is,

Δ U = Q + W

Where,

ΔU = The total amount of change in internal energy of an ideal gas in a system

 Q = The amount of heat transfer between the system and the system’s surroundings

 W = Work done by a system

In some process there is no change in internal energy. The processes are cyclic process, isothermal and free expansion. In these processes the amount of internal energy is same because the temperature of the system remains unchanged.

How to calculate change in internal energy of an ideal gas?

From the 1st law of the thermodynamic we can a concept about change in internal energy of an ideal gas.The amount of internal energy of an ideal gas is equal to the heat flow and PV workdone by the system.

The quantity of the internal energy that could be change for a gaseous matter that always should be equal to the workdone of the system and the amount of input heat and amount of output heat.

Formula for calculate change in internal energy of an ideal gas:-

Q =ΔU = W…….eqn (1)

Q = ΔU + PV

Because we know that, the amount of heat is added or removed is always equal to the total sum of the internal energy which is changed and the workdone of PV.

From the eqn (1) after arranging we get,

ΔU = Q – PV……. eqn (2)

Frequent Asked Questions:-

Question: – Is all-time the values of the internal energy of a substance remain positive or it can be negative?

Solution: – No, all-time the values of the internal energy of a substance cannot remain positive.

Some time the value of the internal energy can be negative. We can calculate the value of internal energy from the sum of workdone and heat. Negative value of internal energy of an ideal gas means the value of final energy is low than the value of initial energy.

Question: – Give some examples of internal energy.

Solution: – Some examples of internal energy listed below,

1. Vapor of a liquid substance
2. Shaking of a liquid substance
3. Batteries
4. Compressed gasses
5. Increasing the temperature of a substance

This article discusses about examples of heat transfer. Heat transfer is a branch of thermal engineering that concerns with generation, use and exchange of heat energy from one system to another.

Heat can be transferred by many ways. Most commonly known methods are conduction, convection and radiation. This article discusses about different modes of heat transfer and then we will discuss about examples of heat transfer that we see in our daily lives.

• Our skin gets warm after going out in sunlight
• Boiling water
• Thermometer
• We get burned after touching hot pan
• Water gets warm after leaving under hot sun
• Food gets warm after heating it in microwave
• Food gets cold when left in room
• Tea cup gets hot after tea is poured in the cup
• Phone gets hot when its battery gets hot
• Phone charger gets hot when the wires inside get hot
• TV gets hot after its coil gets hot after excessive usage
• Forest fire
• Ice melts after being dipped in a warm drink
• Steamer

What is heat transfer?

As discussed above, heat transfer is the branch of thermal engineering which deals with generation of heat, use of heat and transfer of heat through various physical systems.

Heat does not necessarily need a medium to get transferred from one system to another. These systems are at different temperatures. The heat will flow from a system with high temperature to a system that is at lower temperature. We shall study about its types in the later sections of this article.

Image credits: Kmecfiunit, cmglee, Heat-transmittance-means2, CC BY-SA 4.0

Modes of heat transfer

The heat can be transferred from one system to another by many ways. Some methods need a medium whereas some methods like radiation don’t need any medium for heat transfer to take place.

The different methods of heat transfer are given below as follows-

• Conduction – Conduction is a mode of heat transfer where the heat s transferred through systems when they are in contact with each other. The molecules of these systems vibrate and transfer energy through these vibrations. The vibrations although fade away as the distance becomes larger proving that conduction is inversely proportional to the length of the systems.
• Convection – Convection is the process of heat transfer with the help of moving fluids. When we pour warm water on our body and our muscles get relaxed, this is due to convection of heat from water to our skin.
• Radiation – Radiation is a process of heat transfer in which the heat is transferred without the help of any medium or physical contact between the systems.

Examples of heat transfer

Heat transfer takes place almost everywhere around us in daily lives. The most commonly seen examples of heat transfer are given below-

Our skin gets warm after going out in sunlight

The heat emitted by the Sun gets radiated towards Earth. This radiated heat is absorbed by our skin and hence we feel warm when we go outside in sunlight. Long exposures may even burn the skin (tanning is an example).

The steel spoon gets warm after coming in contact with hot container

When the steel spoon is kept in touch with a hot container, the steel spoon gets warm due to heat transfer by conduction. As the steel spoon is a good conductor of heat, the heat gets easily transferred to steel making the steel spoon’s temperature higher.

Boiling water

The water is boiled due to convection and conduction both. The vessel inside which the water is kept becomes hot first. This is due to conduction heat transfer. Then the water gets heated as a result of heat transfer between the water surface and the hot vessel. The remaining water gets hot by the process of convection.

Thermometer

In thermometer, the level of Mercury rises when the heat from body is transferred to it. The rise in Mercury is used to determine the temperature of our body.

We get burned after touching hot pan

When the pan is hot and we touch it, we feel hot or burn our hands sometimes. This is due to heat transfer taking place due to conduction. The heat from hot pan is transferred to our skin as we make contact to the pan.

Water gets warm after leaving under hot sun

When we leave water under hot sun, the heat radiated by the Sun makes the water warm. This happens so because the water absorbs the radiated heat which in turn makes it warm. This is the same reason why we feel hot after stepping outside the house under scorching heat.

Food gets warm after heating it in microwave

Microwave is used for warming the food. The microwave sends out waves which makes the food warm. This entire heat transfer process takes place in the form of radiation.

Food gets cold when left in room

When we leave the food untouched in our room, then the food tries to make thermal equilibrium with the surroundings which happens by lowering the temperature of food. As the food gets colder, thermal equilibrium is established. This is also an example of heat transfer as heat is transferred from the food to surroundings.

Tea cup gets hot after tea is poured in the cup

After tea is poured in the cup, conduction takes place between the outermost layer of tea and the surface of the cup. This way the heat is transferred from tea to the cup as a result of which the cup becomes hot.

Phone gets hot when its battery gets hot

When the battery gets hot due to longer operation of phone, the phone also gets hot. This is because the battery is in contact with the mobile phone. The heat is transferred from battery to the phone with the help of conduction.

Phone charger gets hot when the wires inside get hot

The wires inside a charger adaptor get hot due to excessive charging. These wires are in contact with the adaptor from inside, this way heat transfer due to conduction takes place and adaptor in turn also becomes hot.

TV gets hot after its coil gets hot after excessive usage

After excessive usage, the coils inside TV get hot. The coil being in contact with the inside of TV, makes the tv also hot. This is why it is recommended to watch television under control.

Forest fire

When the heat from sun is very strong, the dry leaves may catch fire due to excessive heat. This is an example of radiation heat transfer. It is important to note that radiation can cause fire too!

Ice melts after being dipped in a warm drink

After dipping the ice in a warm drink, convection takes place between ice and the drink which makes the temperature of ice higher. This result in melting of ice.

Steamer

Steamer is a device that emits out steam. This steam is used for getting rid of cold or skin treatment etc. The heat from the steam is transferred to our skin with the help of convection. The steam carries the heat with it and transfers it to the skin when in contact with it.

Examples of heat transfer by radiation

Radiation heat transfer does not physical contact of both the systems nor it needs a medium to get the heat transferred from one system to another. Let us see some of the examples of radiation heat transfer given below-

• Hot metal rod transferring heat to surroundings – When a metal rod is heated, it emits out heat to its surroundings, this heat transfer takes place with the help of radiation. If we put our hand near the metal rod, we will feel hot even without touching it.
• Microwave – Food is warmed inside a microwave by the action of heat transfer by radiation. The microwaves inside the microwave make the food warm with the help of radiation.
• Solar UV radiation – Solar UV radiation is the radiation emitted by the sun. This radiation can be used for generating electricity using solar panels. Even our skin gets warm due to the action of UV radiation. This is solely due to heat transfer by radiation.
• Emission of Gamma rays – Gamma rays are a type of em wave. These waves move by the principle of radiation after being emitted.
• Light being emitted by incandescent lamp -Light from incandescent lamp is an example of radiation as we feel warm while standing beside the lamp even without touching it.
• Heat coming out from bonfire – Bonfire is a small controlled fire used to make ourselves feel warm during cold weather. The heat transfer takes place with the help of radiation. We do not touch the fire of bonfire but still feel the heat being emitted by it.
• Heat emitted by a radiator – A radiator in vehicle becomes hot when the vehicle has travelled too much. The heat emitted from the radiator can be felt by us. This is due to radiation heat transfer. We do not physically touch the radiator but still feel the heat.

Read more about Overall Heat Transfer Coefficient.