Why power is supplied in the form of ac

Alternating current is generated by electrons flowing in alternating directions. Direct current is generated by electrons flowing in only one direction. AC is also called mains electricity, household current, domestic power, line power, or wall power because it is the voltage supplied by a wall outlet. Worldwide, AC voltages range from to V. The rate of direction change is typically 50 to 60 times per second and is designated as Hertz Hz. The two most common frequencies are 50 Hz and 60 Hz.

The equipment designed to use AC tends to require large amounts of voltage, so the voltage is not stepped down as frequently as equipment using DC. DC allows for a constant flow of current to a device. Most smaller electronic devices such as computers require direct current to operate with an AC-to-DC converter from wall power. Alternating current is used for equipment that have motors refrigerators are an example. Which type of current to use depends on the load being powered.

Because unregulated power supplies do not have voltage regulators built into them, they typically are designed to produce a specific voltage at a specific maximum output load current.

These are typically the block wall chargers that turn AC into a small trickle of DC and are often used to power devices such as household electronics. The DC voltage output is dependent on an internal voltage reduction transformer and should be matched as closely as possible to the current required by the load.

Typically the output voltage will decrease as the current output to the load increases. With an unregulated DC power supply, the voltage output varies with the size of the load. It typically consists of a rectifier and capacitor smoothing, but no regulation to steady the voltage. It may have safety circuits and would be best for applications that do not require precision. The advantages of unregulated power supplies are that they are durable and can be inexpensive.

They are best used, however, when precision is not a requirement. They have a residual ripple similar to that shown in Figure 3. A regulated DC power supply is essentially an unregulated power supply with the addition of a voltage regulator. This allows the voltage to stay stable regardless of the amount of current consumed by the load, provided the predefined limits are not exceeded.

In regulated power supplies, a circuit continually samples a portion of the output voltage and adjusts the system to keep the output voltage at the required value. In many cases, additional circuitry is included to provide current or voltage limits, noise filtering, and output adjustments. There are three subsets of regulated power supplies: linear, switched, and battery-based. Of the three basic regulated power supply designs, linear is the least complicated system, but switched and battery power have their advantages.

Linear Power Supply Linear power supplies are used when precise regulation and the removal of noise is most important. While they are not the most efficient power source, they provide the best performance.

The name is derived from the fact that they do not use a switch to regulate the voltage output. Linear power supplies have been available for years and their use is widespread and reliable. They are also relatively noise-free and commercially available. The disadvantage to linear power supplies is that they require larger components, hence are larger and dissipate more heat than switched power supplies.

Although they have more components, they are smaller and less expensive than linear power supplies. One of the advantages of switched mode is that there is a smaller loss across the switch. Because SMPS operate at higher frequencies, they can radiate noise and interfere with other circuits. Interference suppression measures, such as shielding and following layout protocols, must be taken.

The advantages of a switched power supply is that they are typically small and lightweight, have a wide input voltage range and a higher output range, and are much more efficient than a linear supply.

However, a SMPS has complex circuitry, can pollute the AC mains, is noisier, and operates at high frequencies requiring interference mitigation. Battery-based Battery-based power is a third type of power supply and is essentially a mobile energy storage unit. Battery-based power produces negligible noise to interfere with electronics, but loses capacity and does not provide constant voltage as the batteries drain. In most applications using laser diodes, batteries are the least efficient method of powering the equipment.

Most batteries are difficult to match the correct voltage to the load. Using a battery that can exceed the internal power dissipation of the driver or controller can damage your device.

Along with the above considerations, the power supply must operate below its maximum rated output current. Loads drawing more current than the adapter is rated for can cause inconsistent results or device malfunction.

Overloading the converter can lead to overheating and ultimately failure, potentially causing a fire hazard or damaging the load itself. While all power supply specifications are valuable, some are more critical than others. A few specifications of note are: Output Current: The maximum current that can be supplied to the load. Load Regulation: The load regulation is how well the regulator can maintain its output with a load current change, and usually is measured in millivolts mV or as a maximum output voltage.

These are typically combined into one measurement. In switching power supplies, the measurement is given in peak-to-peak, showing the extent of the noise spikes that arise from the switching.

Nuclear Fuels. Acid Rain. Climate Change. Climate Feedback. Ocean Acidification. Rising Sea Level. Alternating current Alternating current AC is the type of electric current generated by the vast majority of power plants and used by most power distribution systems. Figure 1. An animation from a PhET simulation [2] of alternating current which has been slowed down considerably.

See direct current for a comparison. Brain et al. How Electricity Works [Online]. A transformer will also be used to raise or lower the voltage to a level appropriate for the device in question.

Not all electrical devices use DC power, though. Many devices, household appliances, especially, such as lamps, washing machines, and refrigerators, all use AC power, which is delivered directly from the power grid via power outlets. Although many of today's electronics and electrical devices prefer DC power because of its smooth flow and even voltage, we could not get by without AC.

Both types of power are essential; one is not "better" than the other. In fact, AC dominates the electricity market; all power outlets bring power into buildings in the form of AC, even where the current may need to be immediately converted into DC power. This is because DC is not capable of traveling the same long distances from power plants to buildings that AC is. It is also a lot easier to generate AC than DC due to the way generators turn, and the system is on the whole cheaper to operate—with AC, power can be hauled through national grids via miles and miles of wire and pylons easily.

DC primarily comes into play, where a device needs to store power in batteries for future use. Smartphones, laptops, portable generators, torches, outdoor CCTV camera systems… you name it, anything battery-powered relies on storing DC power.

When batteries are charged from the mains supply, AC is converted to DC by a rectifier and stored in the battery. This is not the only method of charging used, though.