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What’s the Difference Between AC and DC?

Despite the widespread use of electricity and electronics, people can still get confused between Alternating Current (AC) and Direct Current (DC).

Sure, you know that convenient outlets use AC and power banks use DC. But it is essential to understand the reason behind this and why the two things must not be interchanged.

Basic Concepts: AC and DC

Before discussing the distinctions between the two, it is important to know the basic concepts between alternating current and direct current. These can give us a proper idea to see why both are important and should coexist.

Alternating Current

Electric charge produced in alternating current periodically changes direction. That is, it “alternates” between the positive and negative polarity. This also means that an AC also periodically reverses its polarity due to the alternating flow of current.

Furthermore, generators such as turbines produce high-voltage electrical energy in AC. Since AC can be converted into multiple voltage levels with only the use of a transformer, it is chosen as the primary means to distribute electricity over long distances.

Direct Current

In direct current, electricity only flows in one direction. Unlike the former, DC is best suited for low-voltage applications. This is why direct current is the main choice for most electrical devices such as your phones, and the microcontrollers in your computer’s motherboard.

Additionally, energy stored from all batteries and capacitors flows in DC. However, it is not changing a DC voltage into a lower or higher level is difficult. It requires a bit of knowledge and more components to be able to correctly change the voltage without damaging your components.


Electricity is generated to distribute it to households and establishments. Because generators produce AC on high-voltages, it is the primary choice for electrical transmission over long distances.

The ability of AC to be distributed is based on a few factors.

  • Power loss ‒ it is vital to keep power loss minimal during transmission, and it can be achieved in lower currents that AC provides
  • Materials ‒ since AC can be distributed over long distances under low currents, this adds to the benefit of using thinner wires

On the other hand, DC can also be distributed over long distances. But it requires higher currents and thus needs thicker and more expensive cables. Unlike AC, DC voltage is easier to use in inter-grid connections. These connections are where different power sources are linked together since there will be no frequency issues.


Most power grids around the North Shore are generating electricity through the use of generating turbines. These are large revolving magnets that have alternating polarities at 60 times per second (60Hz).

The movement of its rotor through the surrounding alternating magnetic poles is what generates alternating currents. Thus, making AC the main option for electrical generation. The primary medium that makes turbines spin is steam. Steam is produced from:

  • Coal-fired power plants
  • Gas turbine
  • Biomass combustion
  • Cogeneration

Additionally, other generation methods that use turbines include:

  • Wind farms
  • Hydroelectric power
  • Gas Reciprocating Engines

DC, on the other hand, is a constant and non-periodic current. The only way to generate a constant direct current is through the chemical reaction of 2 dissimilar metals submerged in an electrolyte, in short, a DC cell. 

The first DC cell model was made by piling up copper and zinc discs, separated with paper soaked in mild acid solution ‒ called a voltaic pile. This produces a steady current flow in a circuit and was developed to become today’s battery cells.

DC is produced for distribution in Solar Farms. This method uses photovoltaic cells to convert sunlight into DC electrical energy. The generated electricity is then converted into AC and increased in voltage before connecting it to the grid for transmission.

Power Factor

Power factor is the expression of energy efficiency as a percentage. A lower percentage means lower efficiency. It is also defined as the ratio between working power and apparent power.

Working power is measured in kilowatts (kW), and apparent power is measured in kilovolt amperes (kVA). Additionally, working power is the power absorbed by the load. In contrast, apparent power is the amount of power needed to run an electrical load.

Moreover, alternating current has a power factor ratio between zero (0) and one (1). On the other hand, the direct current always has a power factor of one (1), meaning DC has better efficiency than AC.


Both AC and DC have different pros and cons. However, one should coexist with the other, since AC is the choice for long-distance transmission, and DC is used to power your daily appliances.

Besides, a better understanding of both currents will help you avoid unexpected electrical emergencies. Remember to use appropriate power adapters when plugging in low-voltage appliances/devices such as a Wi-Fi router or desktop computers to your wall outlets.

Finally, it is important to keep your electrical system fault-free. A worn-out power outlet might short or overload the moment you plug in your gaming rig or home entertainment system. Sydney North Shore Electrician will help you maintain your electrical system and replace worn-out components.

Call us at (02) 8378 2828 to experience 24/7 expert-level service.

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