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Alternating Current (AC) vs Direct Current (DC) Power: An HVACR Guide

HVAC Technician

Are you interested in becoming an HVACR professional? While attending an HVACR program at a vocational school, you will have the opportunity to study alternating current (AC) and direct current (DC). This knowledge will come in handy when working on heating, ventilation, air conditioning and refrigerators.

In the 1880s, the electrical industry was in a state of disarray. In the early years of electricity, direct current could not be easily converted to high voltages and powerplants needed to be established within one mile of the end user. Alternating current, on the other hand, could be provided relatively inexpensively at several thousand volts with little loss of power as it traveled to the end user. As opposed to DC, an AC power plant could be located several miles away from the end user. With Thomas Edison holding patents on DC power at the time, a current war was sparked.

The War of the Currents

The War of the Currents began in the 1880s with Thomas Edison and Nikola Tesla. As reported by the Department of Energy. Tesla believed that alternating current was necessary to phase out kerosene, which up until the introduction of electricity, had been used to light lamps and heat cookstoves. As Telsa championed AC, Edison fought back with his patents on DC.

The final battles of the War of the Currents took place at the Chicago World’s Fair in 1893 and the powering of Niagra Falls in 1896. General Electric lost both bids to Westinghouse, who purchased AC patents from Tesla. For over a century, AC has dominated the electricity industry but in recent years, DC has become vital for the use of electronics such as TVs, LEDs and computers.

With the invention of semiconductor electronics, conversions between AC and DC have become economically possible. Advances in electricity has made direct current more stable, and with its minimized power loss, more and more companies today are using it to transport electricity over long distances.

Alternating Current (AC)

In the US, alternating current reverses direction 60 times per second. This enables it to be easily converted into different voltages using a transformer. AC can be produced with the use of an alternator in which a loop of wire is spun inside of a magnetic field. The magnetic field induces a current on the wire with the rotation of the wire coming from either a turbine or flowing water. The wire spins and enters a different magnetic polarity periodically causing the current to reverse direction 60 times per second. In a set of water pipes, AC can by generated by connecting a mechanical crank to a piston that shifts water back and forth.

Direct Current (DC)

Direct current was aptly named because the electric charge only flows in one direction. Today, most of our electricity is powered by alternating current, but gadgets such as computers and electric vehicles rely on DC power. To generate DC, a device called a rectifier is used to convert AC to DC. Batteries also provide DC power, generated from a chemical reaction which occurs internally.


As both AC and DC are necessary to power everyday appliances such as refrigerators and air conditioners, it is vital for HVACR professionals to understand how they function and provide power.

Do you want to develop the skills to be a successful HVACR Technician? Does a career as an HVACR Technician interest you? MIAT’s HVACR Technician Program is 9 months in length for full-time students, assuming there are no interruptions in training, and is offered at both the Michigan and Texas campuses. MIAT provides training that allows students to focus on their chosen field, earning their certification faster than a traditional 2 or 4-year college degree or 3 to 5-year apprenticeship.

To learn more about HVACR Technician career training and to explore if MIAT is right for you, fill out the form on this page.

MIAT College of Technology is accredited by the Accrediting Commission of Career Schools and Colleges (ACCSC).

HVACR Technician Program Gainful Employment Disclosure – Canton

HVACR Technician Program Gainful Employment Disclosure – Houston

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