There are different forms of energy and one form of energy
There are different forms of energy and one form of energy can be converted into another. When we light a wax candle, the process is highly exothermic and on burning, the chemical energy of the wax gets converted into heat and light. A good source of energy is to be selected for the choice of work to be done.
In ancient times, wood was the most common source of heat energy. We, in our daily lives, use various energy sources for doing the work. Nowadays we use diesel and electricity to run trains. We also use fossil fuels in vehicles which has some serious disadvantages, mainly air pollution. The recent example of air pollution was ‘Smog’ in the National Capital Region of Delhi. This pollution was a result of burning ‘Parali’ in northern states of the country, which affected the eyes and also caused serious respiratory problems.
4(a) State the energy conversion that takes place when we light a wax candle. 1
4(b) List two criteria of selecting a source of energy for a specific work. 1
4(c) Write the names of two fossil fuels. 1
4(d) Why are we looking at alternate sources of energy ?
Answer
- Chemical energy to heat / light energy
- i. high calorific value ii. be easily accessible iii. ability to do a large amount of work per unit volume or mass iv. be easy to store and transport v. Be economical (any two)
C. Coal, Petroleum, Diesel, LPG (any two)
D. 1. Increasing demand with industrialisation and changing lifestyles
2. Fossil fuels are in limited quantity and will be exhausted