This type of coma is usually reversible once the blood sugar is corrected. Oxygen deprivation: Oxygen is essential for brain function. Cardiac arrest causes a sudden cutoff of blood flow and oxygen to the brain, called hypoxia or anoxia.
The external power supply is the AC power adapter that converts household AC electricity voltages to the much lower DC voltages needed to charge a mobile phone's internal battery.
The final energy (12.6 J) is equal to the initial energy (0 J) plus the work done by external forces (12.6 J). In each of these examples, an external force does work upon an object over a given distance to change the total mechanical energy of the object. If the external force (or nonconservative force) does positive work, then the object gains mechanical energy.