Activity 14.7 NCERT Class 10 Science, Sources of Energy
The energy source can be wind, biomass, ocean, etc. Activity 14.7 asks us to discuss the actual ultimate source of energy and compare them with geothermal, and nuclear energy.
The ultimate source of energy
We get energy from various sources like electricity, cooking fuel etc. These sources of energy come from other sources of energy. A thermal plant uses coal to produce electricity, a hydroelectric plant using the energy of stored water and so on. If we go into the depth of the actual source of energy, we find that all these energies are derived from the sun. Let us discuss this in detail.
We use the energy of air flow to generate electricity in a wind power plant. Sometimes we also use wind energy to grind grains in a windmill. In older days and still, people sail through the river and ocean using wind energy in their boats.
What causes the wind to blow
Sun provides us with energy in uneven condition. In the night a part of earth doe not receive sunlight while at the same time another part of the earth faces the sun; equatorial region receives scorching sunlight while polar region receives minimal sunlight. This uneven distribution of sunlight warms the atmosphere unevenly. Air have convection property. Hot air tends to move toward cold condition while cold air tends to move toward the hot region. This results in the movement of air, which we call wind. Thus the ultimate source of wind energy is the energy of the sun.
Biomasses are the organic compounds obtained from life sources such as plant and animal remains. We use them in a biogas plant to produce methane. Methane gas is highly inflammable and finds its use as cooking gas.
In recent scientific development, scientists can produce ethanol and other organic compounds from plant sources. Works are going on to uses these compounds as fuel for vehicles and industries. We call such fuels as bio-fuels.
The ultimate source of energy in biomasses:
The plant produces its biomass using the energy of sunlight by Photosynthesis. Thus the actual source of energy here is also sunlight.
Ocean thermal energy:
Ocean thermal energy is the energy of the surface of the water. Sunlight heats the surface of the water. This heated water is used to run turbines and generate electricity. Thus, here also the sun is the ultimate source of energy.
Comparison of the sun with Geothermal and nuclear energy
Earth inner surface is hot. We call this heat energy Geothermal energy. The source of this energy is the radioactive decomposition of nuclear materials. So, here the sun is not the ultimate source of energy.
We get nuclear energy from the radioactive decomposition of radioactive material like uranium and plutonium. It is similar to geothermal. The only difference here is that it is artificially done by us in a nuclear reactor. So, here also the sun does not have any role in proving energy to geothermal or nuclear energy.
The energy we use come from various sources and forms. Most of them deriver their energy from the sun like solar energy, biomass energy, wind energy, hydro energy, ocean thermal energy. Only a few energy sources do not have the sun as their ultimates source. These are atomic energies in some radioactive elements.