List any four sources of energy which are selected for use for a given activity.
1. Energy to run a cycle
2. Energy to run a car
3. Energy to cook food
4. Energy to work on
Four sources of energy used in the activity is:
1. Energy of muscles
2. Chemical energy of petrol or diesel
3. Chemical energy of gas or kerosene
4. Electrical energy obtained from potential energy. Electrical appliances of water, chemical energy of fuels etc.
What are the characteristics of a good source of energy?
Characteristics of a good sources of energy are:
(i) it should give an adequate amount of net energy or work per unit volume or mass,
(ii) it must be convenient to use so as to give energy at a steady rate,
(iii) it must be easy to store and transport,
(iv) it must be economical, and
v) it must be easily accessible.
The raw materials that provide the requisite amount of energy to perform various functions of life are called sources of energy.
(i) We need heat energy to cook food.
The various sources are: Fuels, wood, coal, kerosene, cooking gas etc.
(ii) We need energy for our transport.
The various sources are: Petrol, diesel.
(iii) We need energy to light bulbs, tubes, to run radio, television and other power appliances.
The source is electricity.
(iv) Production in factories and agriculture also need energy.
The source is diesel and electricity.
Explain the classification of different sources of energy?
Energy sources can be classified as:
(i) Non-renewable resources: The sources of energy which are produced under special circumstances over millions of years due to slow changes. The process involved is not continuous.
E.g., Fossil fuels like coal, petroleum and natural gas are non-renewable energy sources. With the present rate of their consumption, it is estimated that known deposits of petroleum in our country will be exhausted in another 200 years and that coal may last for another 250 years.
(ii) Renewable sources: The sources of energy which can be harnessed into energy so long as the earth derives its heat and light from the sun are renewable sources.
E.g., flowing water, wind, tides, ocean waves and biogas are examples of renewable sources. Wood is also a renewable source of energy.