by Francis Jock

Created on: August 14, 2008

Direct current and Alternating current are common terms used to describe the two forms of electricity we use every day in countless different situations. These terms are applied to many different types of devices we have come to take for granted in our age of technology. DC devices are sometimes battery operated, although it has become quite common to convert AC to DC by a converter. AC devices, such as household appliances and power tools, use considerably more electricity and are plugged into the familiar AC outlet.

You probably buy many different types of batteries, which supply DC to operate low-voltage devices such as your calculator, cell phone, TV remote control and even to start your car. DC batteries can be quite small and made and named by the different chemicals that make them work. For instance, a 12-volt car battery is a "Lead-Acid" battery, and common dry cell batteries come in sizes ranging from AAA to D. Many low voltage devices use batteries made from Nickel-Cadmium (NiCad) or may be Lithium-Ion batteries. Each type of battery supplies a direct current at a specific voltage and may be rechargeable, recyclable, or disposable.

Alternating Current devices require more electrical power to operate than DC devices. Some examples of AC devices include microwaves, toasters, washers and dryers, power tools and your computer. Electronic devices, such as your television, entertainment system, and computer have internal power supply circuits that convert and regulate household 120V AC to different amounts of DC as required. Other devices, such as your garage door opener, air conditioner and refrigerator use AC to run an AC motor, which drives some mechanical device such as a compressor, or simply perform work for us.

In a conventional explanation of direct current, direct current can be described as the uninterrupted and constant flow of electricity from a point of negative electromotive force to a point of positive electromotive force. There are many different types of batteries used to store electricity and serve as the source of electromotive force. For example, a 1.5 Volt AA battery will supply an electromotive force, or difference of potential, of 1.5 volts when measured across its positive (+) and negative (-) terminals.

When the terminals are connected in a closed loop with an electrical conductor, such as a copper wire, an electrical current will flow between the terminals as long as the difference of potential remains. The battery and the wire, now

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