ENERGY

ENERGY
ENERGY
“The ability of a body to perform work is called Energy”.
A body cannot perform work if it does not posses energy. A body cannot perform work more than the amount of energy.
It is a scalar quantity.
UNITS OF ENERGY
(i) Joule
(ii) Calorie [NOTE: 1 Calorie = 4.2 joule.]
(iii) KWatt-Hour
TYPES OF ENERGY
There are numerous types of energy such as:

  • Heat Energy
  • Light Energy
  •  Sound Energy
  •  Nuclear Energy
  •  Chemical Energy
  • Electrical Energy
  • Solar Energy
  • Wind Energy
  • Kinetic Energy
  • Potential Energy etc. etc.
POWER
“The rate of work done of a body is called Power”.
AVERAGE POWER
Average power of a body doing work is numerically equal to the total work done divided by the time taken to perform the work.
Mathematically
Power = Work done/time
Power = Work/t
but [work = Fd]
therefore
Power = Fd/t
UNITS OF POWER
(i) watt [1 watt = 1joule/sec ]
(ii) Kilo watt [1Kw = 1000 watt]
(iii) Mega watt (Mw) [1Mw = 106 watt]
(iv) Horse power [1Hp = 746w]
POTENTIAL ENERGY
INTRODUCTION
Energy stored by a body by any means is called “Potential Energy”.
DEFINITION
“The energy stored by a body due to its position in gravitational field is known as ‘Gravitational Potential Energy’”.
FORMULA
Consider a body of mass “m” placed at a height of “h” from the surface of earth.
Force = Weight = W
but displacement (d) = h
Gravitational Potential Energy
Work done = Fd
OR
Work done = Wh
[but W = mg]
work done = mgh
WE know that the work done in lifting the body is stored in the body in the form of Potential Energy. Thus, P.E. = mgh