Electrical Circuits & Network Theorems: Work, Energy And Power

Definition Of Work, Energy And Power | Principal Of Conservation Of Energy

WORK:-

Work is done whenever an object moves in a field of force, F (unit of force is Newton, N). If the object moves in the direction of force, work is done by the force.

However, if the object moves in a direction opposite to the force, work is done by an external agency that moves the object.

ENERGY:-

It is the capacity for doing work. when a weight is lifted against gravity, work done by an external agency in lifting it gets stored in the weight as potential energy(by virtue of its position in the gravitational force field).

If the weight were now allowed to fall the potential energy will get converted to kinetic energy (associated with velocity).

Further, if the weight were to fall on a wedge, it will drive it into a piece of wood(say) thereby doing work. The process of doing work in some sense is a process of energy transfer.

In the example cited above energy is transferred from the external agency to the weight and get stored as potential energy. When the weight falls, it still remains stored in the weight but gets converted to kinetic energy. Upon hitting the wedge, it gets transformed to heat in driving the wedge against wood friction.

Energy, W is measured in unit of Joules, J Or Newton-Metres, N-m, as it equals force N X Distance Moved (m).

PRINCIPLE OF CONSERVATION OF ENERGY:-

In Non-relativistic processes energy never gets destroyed; it gets converted from one form to another as illustrated in the above example.

Power

It is the rate of doing work(i.e., rate of transferring energy). Instantaneous power is