Energy makes things occur around us. There are different types of energy we keep using in our daily lives. In day time we use energy from sun in the form of heat and light whereas in nighttime, we get light in the form of electrical energy from streetlamps and bulbs. When a car moves on the road, it uses a stored energy form called gasoline. Similarly, when we play or work, we use the energy we get from the food we eat.
We already learned about energy in our previous post of introduction that Energy is the capability to work. As said earlier, energy is categorized into various forms like light energy also called radiant energy, chemical energy, mechanical energy, nuclear energy, and most common heat energy also called thermal energy.
Types of Energy
Energy is divided into two main types which are Stored Energy and Moving Energy. The other names of these kinds of energy are Potential Energy and Kinetic Energy respectively.
These two major types can be best explained with an example of a stick. Place a stick on the rim of a desk and then push it off to the floor. The stick comes in state of using kinetic energy to move from desk to the floor. On other hand, you pick up the stick and place it back to its position on the desk where it rests; the stick uses the potential energy to stays in its position.
How to Measure Energy?
The second point to know is how energy is measured. Energy is measured in many ways. The basic measuring block is Btu which stands for British thermal unit and was invented by the English. The Btu is defined as the amount of heat energy to raise the temperature of one pound of water at one degree Fahrenheit, at the sea level. It takes about 2,000 Btu to prepare a pot of coffee. Another unit to measure energy is Joules. The unite joule came into being by the scientist James Prescott Joule who discovered that heat is a form of energy. With respect to Btu.
A thousand joules is equal to one Btu i.e. 1 Btu=1000 joules.
Thus 2 million joules are required to prepare a pot of coffee. One joule is defines as the amount of energy require to lift something that weights one pound to the height of nine inches.
Usually around the world, scientists prefer using the metric systems of meters and kilograms rather than feet and pounds. Likewise, scientists use joules in measuring energy as compared to Btu. Thus, by using the metric system, 1000 joules can be counted as Kilojoules as 1 Kilo=1000.
So, 1000 joules=1 Kilo joule=1 Btu.
Transformation of Energy
It is a fact that energy can be changed from one form to the other, but it cannot be created nor destroyed. The conversion of energy from one form to other is easy to observe. Like when we eat food, we store energy as potential energy, and we work or move or do some movement, the potential energy changes to kinetic energy. Similarly, the car stores chemical energy as gasoline before it moves. When the car moves, the gasoline is converted into heat by engine and powers car to move by kinetic energy. One better example to see is when we turn on TV, the electrical energy changes into light and sound energy forms.
The Energy in Food
It is understood that energy keeps changing in different forms. Thus it keeps changing every next step in food chain. This is how it happens:
The sunlight is absorbed by the leaves of the corn stalk; it is than transformed by the photosynthesis, the plant gets the carbon dioxide from air, minerals and water from the soil to grow up. The plant grows and gives corn seeds. The sunlight energy is stored in the leaves of the plant and the sugar and starch in the seed kernels. These seeds are later on harvested by the farmers and fed to chicken and other animals. The energy in the corn seeds is taken by the chicken and it uses to move and grow. Most of the energy is saved in the animal’s muscle tissues (protein) and in fat. The chicken when is fed properly, it gets mature and the farmer slaughters it. Its meat is sold in the market place from where your parents buy it, get it home and cook it on their own energy.
After cooking, you eat the chicken’s meat and the energy that was stored in the chicken now gets into your body. If you are having meal at a picnic, the energy you get from the chicken’s meat is used by you when you play, run, jump or do other activity. When you breathe, you exhale carbon dioxide which once again is used by the plant leaves to grow. In this way the food cycle keeps going on and the form of energy keeps changing.
One of the most common and important form of energy is heat energy. It is used to warm homes and cook food and do many other works that require heat. Heat in the form of energy moves in three different ways, these are:
The term conduction means heat is transmitted directly from one place to another.
An example of spoon and pan will best explain it. When we stir a pan of hot soup with a metal spoon, the heat of the soup gets transfer to the cold part of the spoon and makes it hot as well. This is the reason why metals are called good conductors of heat whereas plastic and glass are counted as bad conductors. That is why the pan and other cooking pots are made of metal and the handle is of wood or strong plastic.
The second type is Convection, in which gases and liquids move from colder place to warmer place.
When a soup is heated, with time, the warmer soup goes up at the top from the bottom and the cold part of the soup takes its place in the bottom of the pan. This is a circular movement and can be easily observed in the glass pan.
The third and the final part of the heat movement is Radiation. The heat and light that sun emits, cannot reach us directly.
As there is no medium in between us and sun, therefore no conduction or convection can take place and that the space is almost empty. So, light travels from sun to the earth in the form of rays. This movement of rays is called radiation. When sunlight reaches the earth, it is either absorbed or reflected. The darker portion on earth absorbs more sunlight and lighter areas reflect the sunlight. This explains that if you wear light or white color in summer you will stay cooler.
More on Energy in next post…