Work - thermodynamics:
The work can be defined as follows:
"Work is defined as energy transferred across the boundary of a system due to an intensive property difference other than temperature which exists between systems and surrounding."
The difference in pressure results in mechanical work and difference in electrical potential results in electrical work.
"Work is done by the system at the time of given operation if sole effect of the system on things external to the system (surroundings) can be reduced to rising of weight".
The work is positive when done by system and negative if work is done on system.