WORK, POWER & ENERGY

WORK :

Work is said to be done by force F when the point of its application moves Mathematically, through a distance S.

Work = force x distance

           = F x S

an acceleration of one The unit force in the mks system is newton (N). defined as the force acting on one kilogram mass of a body for one second which gives metre per second.

If in the above equation,

. force = 1 N and distance = 1 m, then

Work done = 1 N-m or joule (J)

In the mks system of units, work done is given in joules. It is defined as the work done by a force of one newton when the point of its application moves through a distance of one metre in the direction of the force. Therefore

1 J = 1 N-m

POWER :

 Power may be defined as the rate of doing work. Mathematically,

work done Power time

Note : Work done or energy expanded = power x time. If in time t sec, a quantity of electricity Q is transferred between the ends of a conductor when a potential difference is V, then 

Work done per second = VQ/t

But. Q = I x t

.    Q/t = I

Power = V x I

In the MKS system, the unit of power is the watt. It is denoted by the letter W.

1 W 1 J/s = 1 N-m/s.

 WATT :

It is a unit of electrical power. A watt is equal to the energy expanded per second by current of one ampere under the pressure of one volt. It is denoted by the letter W and is measured by wattmeter.

The electrical power or wattage of a machine can be obtained by multiplying the current in amperes by the pressure across the terminals in volts.

Wattage  = voltage x current   

.            W = V x I

ENERGY :

Joule is the smaller unit of energy. It is the energy used in a circuit when one watt has been absorbed for one second. One joule is therefore equal to one watt second.

Watt second or joule = watt x time in seconds