Ever Wonder About Direct Current?
When an electrical charge travels one-way it is called direct current (DC). Alternating current (AC) travels back and forth, back and forth, over and over before it reaches it's destination. A power inverter changes the flow of the charge from direct current to alternating current. A rectifier does the opposite, changing alternating current to direct current. Some examples of direct current producing sources are batteries, thermocouples, solar cells, and commutator-type electrical machines of the dynamo type.
Batteries already have DC energy stored and ready to use in an electrical appliance. If the power from the battery needed is alternating current, then a dc to ac inverter is required. A thermocouple is a widely used form of temperature sensor and can also be used to convert heat into electrical power. Solar cells convert light directly into electricity by what is called photovoltaic effect. This type of energy is referred to as solar energy. A dynamo, formerly known as an electrical generator, is now better known as a generator that produces direct current. Dynamos were a breakthrough because they were the first electrical generators that could deliver power for industry, and were the cornerstone for the creation of the electric motor, the alternator, and the rotary converter. Because of the dominance and efficiency of alternating current and solid state rectifiers to convert the energy to direct current, dynamos are rarely used today.
Direct current can travel in several ways. It can travel on a conductor, which is generally some form of metallic wire such as copper or aluminum. The wires, or conductors, can also be protected by insulators that resist the flow of electric current, thus allowing multiple currents to travel along different conductors in close proximity. A semi-conductor is kind of a combination of a conductor and an insulator in one. A very wide variety of electronics implement the use of semiconductors. Silicon is a very popular substance used in the making of semiconductors. The current travels by way of electrons or positively-charged "holes" in the electron structure of the silicon. Direct current can also travel through a vacuum as in electron or ion beams. A light bulb is a great example of a simple form of vacuum that electricity travels through.
Direct current is used for a variety of things such as charging batteries and used in almost all electronic devices as the power supply. In some urban areas it is used to propel railways. The production of aluminum uses very large quantities of direct-current power. Large amounts of power are transmitted via high-voltage direct current from remote generation sites or to interconnect alternating current power grids. Typically the power being transmitted from a power generation site is in alternating current. However, over long distances direct current is more efficient as less power is lost and is transmitted at a lower cost.