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# Energy Conservation

Most of the physical and chemical process are completed by energy changes. This energy change may take place in the various forms like heat, work, electrical energy etc. All these form are quantitatively related to each other. The thermodynamics involve the study of these various forms and their relationship. The thermodynamics is based upon three laws. These laws can apply to only equilibrium systems or systems which move from one equilibrium state to another state.

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## What is Conservation of Energy?

"The amount of energy in a system will stay constant whole time. It does not depend upon the amount of matter. Energy is able to transform into some other different form like a chemical energy can become kinetic energy but nothing can destroy the energy. "

There are many other forms of energy. For example, potential energy (it is the energy of location with a point), electrical energy (it is created by different charges), thermal energy (it is given off by heat) etc.

So, the energy conservation can be defined as the amount of total energy of the particular system and it is not possible to create and destroy the energy of the system. But it can only be change from one form of energy to another form.

## Law of Conservation of Energy

The first law of thermodynamic is the law of conservation of energy. According to this law statement, the total energy of universe (system and surrounding together make universe) or the energy of an isolated system (the system which can neither exchange energy nor energy with the surroundings) remains constant. But it can be converted from one form to another form. The energy of the whole system cannot be altered or destroyed.

### Justification for the first law

There is not any kind of theoretical proof for this law. This is based only on experimental results. Some observations are given to prove this law which is described as below.

If a certain amount of any form of energy disappears then an exactly equal amount of some other form of energy must be produced. For example,
• The consumed electrical energy is converted into mechanical energy in the operation of electric fan. Similar the electric energy is converted into heat in the heater while in case of bulb, it is converted into light.
• Water can be decomposed into oxygen and hydrogen by an electric current. Approx 285.8KJ energy is required to decompose 1 mole of water. This energy must have been stored in hydrogen and oxygen since same amount of energy in the form of heat is released when 1 mole of water is obtained from hydrogen and oxygen.
Thus, the supplied electrical energy has been recovered as in the form of heat energy.

So the Supplied electrical energy = Heat energy produced.

Thus energy is conserved by changing one form to another form.

### Mathematical expression

This gives the relationship among work, heat and internal energy. The internal energy is the stored energy with in substance or system. The internal energy of system can be increased by two ways.
1. By heat supplying to the system
2. By doing work on the system
If U1 is the initial internal energy of system, after absorbing amount of heat q then the internal energy of system = U1+ q

If w is the work done on the system so the internal energy is equal to

U2 = U1+ q + w
So, U2 - U1 = q + w

This equation shows the first law of thermodynamics where U2 - U1 is the change in internal energy.
• As q and w are not state functions but change in the internal energy or the term q + w is the state function.
• The internal energy of an ideal gas is the function of temperature.
So for the isothermal change ( U2 - U1 = 0) of an ideal gas, the work done by the system is equal to heat absorbed by the system.

## Conservation of Energy

This is a fundamental basic principle of physics. It is related to maintain any quantity constant during any physical or chemical process. In the conservation of energy, the energy remains constant for the whole system. It can’t be generated or altered.

All of forms of energy like potential, kinetic, thermal, electrical etc will remain conserved. All the different energy forms are able to transform into other forms but they are not able to destroy. The energy conservation involves the constant energy of an isolated system.

For example, the solar panels absorb the light energy and convert into electricity because they require light energy for working. Plants take light energy and convert it to chemical energy and form their food.

## Energy Conservation Methods

The energy can be conserved by using some important methods in our daily life especially in home appliances. These are described as below.

Lighting
• Turn off the lights when not in use.
• Use some light colors in curtains to take advantage of day light.
• Use the task lighting rather than bright light. Compact fluorescent bulbs (four times more efficient) and electronic chokes are more efficient and energy saving tools rather than incandescent bulbs and conventional copper chocks.
• The use of electronic regulators is more energy saving than conventional regulators for ceiling fan.
• Use exhaust fans at a higher elevation than ceiling fans.
• Choose iron boxes with automatic temperature cut off system and appropriate regulator. Do not use more water on clothes during ironing.
Kitchen Appliances
• Microwave consumes 50 % less energy than electric or gas stoves.
• Avoid preheating for backing and preparing other items as it consumes more energy.
• Don’t open the microwave door in the mid of cooking as it drops the temperature up to 25°C.
• The use flat-bottomed pans for full contact with the cooking coil can save energy in cooking on electric stove.
• Use moderate flame settings while cooking on the gas stove to save LPG.
• Try to use pressure cooker and lids (for cover the pan) as much as possible in cooking.
• Solar Water Heater is a good energy saving tool than an electric water heater.
• Items like vegetable, milk etc should be taken out of refrigerators before taking in use.
• There should be sufficient space between refrigerator and the walls to circulate the air around the refrigerator
• The use of refrigerator or freezer should be on moderate temperature. The doors should be airtight.
• Make sure about cover all the items in refrigerator as the uncovered foods make the compressor work harder by releasing moisture.
• The smaller cabinets are more useful for storing frequently used items.
Electronic Devices
• Switch off the power of TV, Audio Systems, office equipment, computer etc after taking in use.
• A computer consumes more power than refrigerator (energy efficient).
• Especially the computer monitor, it alone consumes more than half of the system energy.
• The use of computers, monitors, and copiers on sleep-mode when not in use helps to save the energy up to 40%.
• The battery chargers of laptops, mobiles and cameras should be switch off after using them as they draw power and are very inefficient.
• The washing in machine must be with full loads and with sufficient amount of water. The timer facility is very useful for saving energy.
• Always try to use hot and cold water for very dirty clothes and in the rinse cycle respectively. Natural drying process should be preferred than electric dryers.
• The air conditioners with automatic temperature cut off system are more efficient and energy saver. The regulators should be kept at “low cool” position.
• The use of ceiling fan with air conditioners i more effective to spread the cool air and thus it makes easy to operate the air conditioner at higher temperature.
• A roof garden can decrease the load of air Conditioner.
• The lower difference between the inner and outer temperatures makes energy consumption lower.
• The lamps or TV set should be settled away from air-conditioning thermostat as the thermostat takes heat from them and the air conditioner can be run longer than necessary.