Page 1 - LN

SAI INTERNATIONAL SCHOOL
PHYSICS
CLASS IX
Chapter:WORK, ENERGY AND POWER

LESSON NOTES

Transformation of Energy

The change of one form of energy into another form of energy is
called transformation of energy. ...
1. In a thermal power house. Chemical energy——>Heat energy—–
>Kinetic energy-Electrical energy.
2. Electric motor- Electrical to mechanical.
3. Generator- Mechanical to electrical
4. Electric iron- Electrical to heat.
5. Electric Bulb-Electrical to heat to light
6. Steam Engine- Chemical to heat to mechanical
7. Battery or cell- chemical to electrical

More Examples of transformation of energy are as follows-
1. When hands are rubbed, the mechanical energy of hands changes into heat
energy due to friction.
2. When two stones are struck, the mechanical energy changes into heat energy and
sound energy, due to friction.
3. When the blade of a knife is placed against the rotating grinding stone, the
mechanical energy change into heat, light and sound energies.
4. When the brakes are applied on any moving vehicle, the mechanical energy
changes into heat energy as the brakes rub against the moving wheels.
5. When we wind a watch, the mechanical energy of hands change into potential
energy of the spring. When the spring unwinds, the potential energy changes into
kinetic energy and drives the hands of the clock.
6. When an arrow is stretched in a bow the mechanical energy changes into
potential energy. On releasing the string of the bow, the potential energy changes into
kinetic energy of the arrow.
7. Water stored in hydroelectric dams has potential energy. When this water is
released, the potential energy changes into kinetic energy of the flowing water. The
kinetic energy of the flowing water turns the blades of a turbine and drives the
dynamo. The dynamo then produces electrical energy.
8. When a torch is switched on, the chemical energy of the cell changes into
electrical energy, The electrical energy, on passing through the filament of a bulb,
changes into heat energy and light energy.
9. In an electromagnet, electrical energy changes into magnetic energy.
10. The electrical energy, on flowing through the coils of an electric motor or an
electric fan, changes into mechanical energy. It partly changes into heat energy and
hence, heats the coils.