That umbilicus is called a power cord. Also called a main cord, it is a cable that connects an appliance to a power source.
Power cords were first employed in early telegraph systems. They were insulated with Gutta percha insulation which easily rots when exposed to air. Later, Thomas Edison developed a power distribution system using copper rods wrapped in jute cloth and placed in pipes filled with a bituminous substance. Then in 1844, vulcanized rubber, which was developed by Charles Goodrich, was applied to the cords for insulation.
Today, a power cord is composed of two or more electrical conductors. Usually, these conductors are made out of copper or aluminum wire. Electricity travels through the conductors. The conductors are usually arranged in strands for durability and flexibility. However, shorter and smaller power cords can have solidly built conductors.
The strands of wires are wrapped in an insulating sheath. The sheath protects the conductors from dirt, dust and grime. At the same time, it protects the person holding the power cord from the voltage running through the conductor. The insulation is usually made out of rubber. But some heating appliances have cotton fiber as insulators for their power cord. This allows the cord to resist accidental contact from heated surfaces. Rubber and cotton fiber sheathing are enough for power cords that are designed to carry a normal household voltage of 100 to 300 volts.
But some power cords, especially those that are designed to carry very high voltages, are insulated by special materials. For example, cords that carry a thousand volts must be insulated with heavy plastic sheaths which, in turn, are protected with a lead sheath. Some do not even have sheaths. Instead they are buried in the ground, the soil acting as an insulator.
Main power lines that carry around 65,000 volts may have their conductors insulated with oil and paper, and run in a rigid steel or aluminum pipe. This arrangement prevents potentially damaging partial discharges within the cord.
Power cords are not limited to transmitting electricity. Aside from having conductors in them, some cords are also used to transmit data. This is done by incorporating fiber optic strands along with the conductors. This type of power cord is called a hybrid. In the future, it might be possible that we wound not need power cords to transmit electricity. In fact, technology has advanced so much that we can now convert electricity to microwaves and vice versa, allowing a wireless transfer of energy.
However, as of today, it is impossible to view life without this simple but wonderful invention.