House Power Supply: Alternating vs Direct Current

For many, it doesn’t matter how electricity works. What’s important is that it does work. You flip a switch, and the lights turn on, or you plug something into a power socket, and the device operates the way it should.  

However, sometimes you may wonder what the different electrical terms mean and how they relate to the electricity that makes life more convenient for everyone. Or you may be upgrading your appliances and want to know the wattage and voltage of your home’s electrical circuit. Read on if you’re among those who wish to know about direct current, alternating current, and other jargon associated with electric power.  

What is a Voltage?

Voltage is the representation of the pressure that pushes electricity. It is the power that your appliances and electrical devices need to operate. It is what’s in a power outlet that makes it capable of providing electronic devices with the right amount of electricity. 

Volt is the unit measure of voltage, and a voltmeter or voltage meter is used for measuring voltage. The voltage for home appliances varies, but in general, outlets in US homes are either 120 or 240 volts.  

What is a Current?

Electric current is the rate at which electrical charge carriers like electrons flow past a point in a complete electrical circuit. Electrical current typically flows from negative to positive ends. 

The ampere or amp is the Standard International Unit for measuring electrical current. It signifies the number of electrons flowing past a point in a circuit over a given time, and 1 ampere of current is defined as one coulomb of electrical charge moving past the specified point. The larger the ampere value, the more electricity is flowing in the circuit. 

Current is widely used in household and industrial applications in the country. 

What is Power?

Power is the rate at which work is done or at which energy is converted to another form, such as heat, motion, or an electromagnetic field. The capital letter P commonly symbolizes power.

Watt (W) is the Standard International Unit of power, which is equal to one joule of work done per second. In some instances, the power of motor vehicles and other machines is expressed in Horsepower (hp), where 1 HP equals approximately 745.7 watts. Meanwhile, in utility circuits, the kilowatt (kW) is often used instead, and 1 kW equals 1000 W. 

What is AC?

Alternating current, also known as AC current or AC, is the flow of charge where the electrons reverse direction several times per second. Consequently, the voltage also moves along with the alternating current. That’s in contrast with direct current or DC power, where the current moves only in a single direction. 

Alternating current is the type of current produced by power plants and is distributed by electric utilities to homes and businesses.  

History

Although the alternating current is the more commonly used current in homes and industries nowadays, direct current actually preceded AC when it came to the use of electricity for industries. In fact, the electrical system in the 19th century ran on DC voltage. 

AC was discovered by the British Michael Faraday somewhere in the 1800s when he noticed that a conductor rotating in parallel within a magnetic field produces a steady electronic flux. Such a flux can be utilized to perform mechanical work. 

Several decades later, Nikolai Tesla, who was working for Thomas Alva Edison’s company, came up with the idea to address the shortcomings of DC power. In 1887, he built the prototype of a motor that generates alternating currents. 

During that time, when the electric current was distributed in the form of DC power, one major disadvantage of the process was that the current heated the electric cables when they traveled long distances. This leads to energy waste and increased costs of distribution. 

In contrast, alternating current can be distributed over great distances without significant energy losses, making it the more efficient current type. 

How Does it Work?

An alternating current is created using a certain kind of electrical generator called an alternator. The rotor, which consists of revolving magnets, and the stator, which is a conductor wound in coils on an iron core, are the components of an alternator. The stator induces an electromotive force in the form of current as it spins, resulting in the production of AC voltage.  

This AC current can change direction periodically, and the voltage in an AC circuit also regularly reverses because the current’s direction changes. 

Alternating current comes in several forms. If an AC circuit is connected to an oscilloscope and its voltage is plotted over time, you will likely see different waveforms. These include the sine, square, and triangle, with the sine being the most common waveform. The majority of mains-wired buildings have an oscillating voltage in the sine waveform. 

Applications of AC Current

Between AC and DC, AC is the more popular current form. It has several applications for homes and industries, which include the following. 

AC for Homes and Offices

Mains-wired structures like homes and offices often work on alternating currents. This is due to the relative ease of generating and transporting AC current across long distances. With a high voltage exceeding 110 kilovolts (kV), less energy gets lost during power transmission.  

That’s because, at higher voltages, lower currents are produced, and lower currents generate less heat in the power line due to a lower level of resistance. As a result, less energy is lost as heat.    

The voltage also remains more stable than that of DC current over time and distance. 

AC for electric motors

AC also works well with electric motors. A motor transforms the electrical energy from AC into mechanical energy, which runs a machine or appliance. Refrigerators, washing machines, clothes dryers, and dishwashers are examples of household appliances with motors that use AC. 

What is DC?

In contrast with alternating current, where the electrons reverse their direction flow periodically, in direct current, the electrons flow only in one direction. This means that instead of oscillating back and forth, the direction and amperage of direct currents stay the same.  

With direct current, the electrons flow from an area of high electron density to a place of low electron density. This is demonstrated in circuits involving batteries by the constant flow of charge from the battery’s negative terminal to its positive one. 

History

Prior to 1870, people lit their homes at night with candles, gas lamps, or lanterns. That changed when Thomas Edison invented the light bulb in 1879. The light bulb ran on direct current, which was produced by dynamos that relied on steam engines to generate the direct current. 

Seeking to corner the electricity market, Edison established numerous direct current generating stations in New York City in the 1880s. He did it through his company, Edison Electric, which later became General Electric. 

DC current paved the way for the practical application of electricity, and with it came the opportunities to power houses, even whole cities. However, DC voltage came with downsides as the power from generation facilities could only travel a short distance (around a mile or so) before it lost too much voltage. That required higher costs and utilization of valuable real estate to deliver power. 

The problems encountered in using DC led to the invention of a motor that generated AC.  

How Does it Work?

Direct current is a relatively simple concept compared to alternating current. With DC, the current flows in only one direction. Even though the current intensity may vary, it will always move in a linear pattern.  

This means that the electrons are driven or pushed from the power generator. They keep moving forward through the wire until they get to the device or appliance, do their work, then continue through the electric outlet to complete their circuit. 

An excellent example of a power source that produces DC is a battery, where the electrons flow from the negative terminal to the positive one. Other examples are fuel cells and solar cells.  

Applications of DC Current

Although AC is the dominant current type used in large-scale electricity distribution, DC still has its uses and is enjoying a renaissance in recent years. 

DC in Electronics

Any gadget with a circuit board uses direct current because the chips inside need a constant, unidirectional flow of electrons to function and store data. Every home PC has a built-in DC converter, which supplies DC-style power to the other components inside the chassis.  

The situation is different with laptops because they have a battery that already provides DC current.  

The bulk of electric motors also requires DC to operate. The motors power everything from a computer’s optical disk drive and hard disk to a robotic arm moving around a production facility. 

DC in Power Generation

The most rudimentary electrical generators produce energy in DC form, which is later converted into AC format for transmission using a transformer. This is because DC generators are easier to build, and they utilize the energy they capture more efficiently. 

Another reason DC generators are more common is that parallel circuitry is much easier to implement with DC than with AC generators, which involve complex engineering and phase-synchronization with devices connected in series with one another. 

Difference Between AC & DC Current

The main difference between AC and DC is the way the electrons flow. In DC, the electric charge or current moves in only one direction. In contrast, the current oscillates or moves back and forth in AC. Also, in DC, the voltage remains constant, while in AC, the voltage periodically shifts from positive to negative and vice-versa.  

So even if both AC and DC can provide power, they have fundamental differences that should be considered in their use. 

FAQs

Conclusion

Both AC and DC provide power to your home. However, they do so in different ways. You get AC from your wall outlets. Your home is also wired to accept AC power. Meanwhile, your gadgets, such as laptops, mobile phones, and wireless headphones, have batteries that supply  DC power. 

Which one is better? They have the same level of importance when it comes to powering your needs. It just depends on what equipment or appliance you need the electricity for. 

Updated on 01-27-23