User:Andraye04/sandbox

Despite DC being mathematically and conceptually simpler than AC, it is actually less widely-used than AC. However, due to the versatility of electric circuits, there are many situations that call for one type of electric current over the other.

Power transmission
AC is almost always used for power transmission to consumers. The reason behind this is the sum of multiple historical and technological details.

Besides solar power, most power generation methods produce AC current. In order to distribute electricity in the form of DC, a rectifier must be used to convert from the initial AC to DC. However, rectification is a complex, expensive, and, until recent, fairly lossy conversion, especially on the scale of power plants. This has made it historically inefficient to convert the AC generated by power plants to DC for distribution.

Along the power lines connecting power stations to consumers, voltage is stepped up and down to reduce heat loss, often multiple times. While DC inherently experiences less heat loss than AC, it cannot be stepped up or down with transformers. This is due to transformers working on the principle of induction: the changing electric field created by AC generates a changing magnetic field, which induces an EMF of higher or lower voltage in the connected power line. DC, however, generally does not fluctuate much, resulting in an unchanging electric field, which generates no magnetic field, making induction impossible. While there is now technology for DC transformers, they are more complex, massive, and expensive than AC transformers, and when infrastructural power grids were being built in much of the world, such technology did not exist.

There are certain cases, however, specifically in high-voltage, long-distance power transmission (HVDC), where DC is used. The main issue with using DC in power transmission is changing voltage for consumers, but this is because the voltage is changed multiple times. For safety, voltage is stepped down the closer it gets to consumers to prevent incredibly high voltage lines from running through highly populated residential areas. However, if constant voltage transmission across long distances is needed, DC outperforms AC. DC carries better over distance and experiences less heat loss, as the skin effect is only observed in AC systems. Additionally, out-of-phase AC systems can only be connected via DC. For example, the U.S. power grid is split into three asynchronous systems. For power to be transferred between any of these systems, DC must be used to mediate the transfer.

Electronic devices
Household electronic devices overwhelmingly use DC. This is due to the nature of basic circuit components. Many essential components in electronic devices, such as transistors, diodes, and logic gates, operate on a one-way basis; the diode, for example, only allows current to flow in one, fixed direction. Trying to use AC with such components would immensely complicate circuit design, requiring designs to function symmetrically with respect to current direction. Additionally, CPU s update millions of times per second, much faster than the mere 100/120 times per second that AC alternates polarities. This would cause massive inconsistencies in CPU performance, meaning all devices that use CPUs must also use DC.

There are, however, devices that are indifferent to current type due to incredibly simple functionality. These devices, such as incandescent lightbulbs or toaster ovens, operate on the basis of running current through high resistance elements, emitting EM radiation. Both AC and DC is affected by resistance, so the current type used is irrelevant, although both types may need to use different voltages to produce identical results.

Education
In university-level EM classes, whether it be algebra or calculus based, DC is typically used as an introduction to electric current. This is due to DC being mathematically and conceptually simpler than AC. A constant, direct current is much more intuitive than one that alternates many times a second. DC power sources are also trivial to add to circuits, both in theory and in practice. For AC, however, phase must be considered when dealing with multiple power sources; whether the phase is off by 0 or π makes a massive difference in the functionality of a circuit. Additionally, circuits with capacitive and inductive elements are very easy to mathematically represent with DC. Charge on a capacitor and resistance on an inductor asymptotically stabilize with time, meaning DC systems reach steady state given enough time. AC, on the other hand, never reaches steady state. The fluctuating current means there will always be changing capacitive and inductive effects in the circuit, complicating mathematical analysis of the circuit. Even as time approaches infinity, the system periodically changes.