File Name: ac and dc theory .zip
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Track My Order. Frequently Asked Questions. International Shipping Info. Send Email. Mon-Fri, 9am to 12pm and 1pm to 5pm U. Mountain Time:. Why, Alternating Current and Direct Current, of course! Both AC and DC describe types of current flow in a circuit. In direct current DC , the electric charge current only flows in one direction. Electric charge in alternating current AC , on the other hand, changes direction periodically.
The voltage in AC circuits also periodically reverses because the current changes direction. Most of the digital electronics that you build will use DC. However, it is important to understand some AC concepts. AC also has some useful properties, such as being able to convert voltage levels with a single component a transformer , which is why AC was chosen as the primary means to transmit electricity over long distances.
Alternating current describes the flow of charge that changes direction periodically. As a result, the voltage level also reverses along with the current. AC is used to deliver power to houses, office buildings, etc. AC can be produced using a device called an alternator. This device is a special type of electrical generator designed to produce alternating current.
A loop of wire is spun inside of a magnetic field, which induces a current along the wire. The rotation of the wire can come from any number of means: a wind turbine, a steam turbine, flowing water, and so on. Because the wire spins and enters a different magnetic polarity periodically, the voltage and current alternates on the wire. Here is a short animation showing this principle:.
Generating AC can be compared to our previous water analogy :. To generate AC in a set of water pipes, we connect a mechanical crank to a piston that moves water in the pipes back and forth our "alternating" current.
Notice that the pinched section of pipe still provides resistance to the flow of water regardless of the direction of flow. AC can come in a number of forms, as long as the voltage and current are alternating. If we hook up an oscilloscope to a circuit with AC and plot its voltage over time, we might see a number of different waveforms.
The most common type of AC is the sine wave. The AC in most homes and offices have an oscillating voltage that produces a sine wave. Triangle waves are found in sound synthesis and are useful for testing linear electronics like amplifiers. We often want to describe an AC waveform in mathematical terms. For this example, we will use the common sine wave.
There are three parts to a sine wave: amplitude, frequency, and phase. V t is our voltage as a function of time, which means that our voltage changes as time changes. The equation to the right of the equals sign describes how the voltage changes over time. V P is the amplitude. The sin function indicates that our voltage will be in the form of a periodic sine wave, which is a smooth oscillation around 0V. This is given in the form of hertz or units per second.
The frequency tells how many times a particular wave form in this case, one cycle of our sine wave - a rise and a fall occurs within one second. As time varies, our waveform varies. Phase is a measure of how shifted the waveform is with respect to time. It is often given as a number between 0 and and measured in degrees. We can turn to our trusty outlet for a good example of how an AC waveform works. In the United States, the power provided to our homes is AC with about V zero-to-peak amplitude and 60Hz frequency.
We can plug these numbers into our formula to get the equation remember that we are assuming our phase is 0 :. We can use our handy graphing calculator to graph this equation. If no graphing calculator is available we can use a free online graphing program like Desmos Note that you might have to use 'y' instead of 'v' in the equation to see the graph.
Notice that, as we predicted, the voltage rise up to V and down to V periodically. Additionally, 60 cycles of the sine wave occurs every second. If we were to measure the voltage in our outlets with an oscilloscope, this is what we would see WARNING: do not attempt to measure the voltage in an outlet with an oscilloscope! This will likely damage the equipment. This is also correct. When talking about AC since the voltage changes constantly , it is often easier to use an average or mean.
To accomplish that, we use a method called "Root mean squared. Home and office outlets are almost always AC. This is because generating and transporting AC across long distances is relatively easy. At high voltages over kV , less energy is lost in electrical power transmission. Higher voltages mean lower currents, and lower currents mean less heat generated in the power line due to resistance. AC can be converted to and from high voltages easily using transformers.
AC is also capable of powering electric motors. Motors and generators are the exact same device, but motors convert electrical energy into mechanical energy if the shaft on a motor is spun, a voltage is generated at the terminals! This is useful for many large appliances like dishwashers, refrigerators, and so on, which run on AC. Direct current is a bit easier to understand than alternating current.
Rather than oscillating back and forth, DC provides a constant voltage or current. The tank can only push water one way: out the hose. Similar to our DC-producing battery, once the tank is empty, water no longer flows through the pipes.
DC is defined as the "unidirectional" flow of current; current only flows in one direction. Voltage and current can vary over time so long as the direction of flow does not change. To simplify things, we will assume that voltage is a constant. For example, we assume that a AA battery provides 1.
What does this mean? It means that we can count on most DC sources to provide a constant voltage over time. In reality, a battery will slowly lose its charge, meaning that the voltage will drop as the battery is used. For most purposes, we can assume that the voltage is constant.
Almost all electronics projects and parts for sale on SparkFun run on DC. Examples of DC electronics include:. Almost every home and business is wired for AC. However, this was not an overnight decision. In the late s, a variety of inventions across the United States and Europe led to a full-scale battle between alternating current and direct current distribution.
Thomas Edison, on the other hand, had constructed DC power stations in the United States by A turning point in the battle came when George Westinghouse, a famous industrialist from Pittsburgh, purchased Nikola Tesla's patents for AC motors and transmission the next year. Thomas Edison Image courtesy of biography. In the late s, DC could not be easily converted to high voltages. As a result, Edison proposed a system of small, local power plants that would power individual neighborhoods or city sections.
Even though the voltage drop across the power lines was accounted for, power plants needed to be located within 1 mile of the end user. This limitation made power distribution in rural areas extremely difficult, if not impossible.
With Tesla's patents, Westinghouse worked to perfect the AC distribution system. Transformers provided an inexpensive method to step up the voltage of AC to several thousand volts and back down to usable levels. At higher voltages, the same power could be transmitted at much lower current, which meant less power lost due to resistance in the wires. As a result, large power plants could be located many miles away and service a greater number of people and buildings.
Over the next few years, Edison ran a campaign to highly discourage the use of AC in the United States, which included lobbying state legislatures and spreading disinformation about AC. Edison also directed several technicians to publicly electrocute animals with AC in an attempt to show that AC was more dangerous than DC.
In attempt to display these dangers, Harold P. In , the International Electro-Technical Exhibition was held in Frankfurt, Germany and displayed the first long distance transmission of three-phase AC, which powered lights and motors at the exhibition. Several representatives from what would become General Electric were present and were subsequently impressed by the display. The following year, General Electric formed and began to invest in AC technology.
Westinghouse won a contract in to build a hydroelectric dam to harness the power of Niagara falls and transmit AC to Buffalo, NY. The project was completed on November 16, and AC power began to power industries in Buffalo.
Alternating Current (AC) vs. Direct Current (DC)
Alternating current AC is an electric current which periodically reverses direction and changes its magnitude continuously with time in contrast to direct current DC which flows only in one direction. Alternating current is the form in which electric power is delivered to businesses and residences, and it is the form of electrical energy that consumers typically use when they plug kitchen appliances , televisions, fans and electric lamps into a wall socket. A common source of DC power is a battery cell in a flashlight. The abbreviations AC and DC are often used to mean simply alternating and direct , as when they modify current or voltage. The usual waveform of alternating current in most electric power circuits is a sine wave , whose positive half-period corresponds with positive direction of the current and vice versa.
Power is the backbone of any electronic system and the power supply is what feeds the system. Choosing the right supply can be the critical difference between a device working at optimum levels and one that may deliver inconsistent results. Direct current power supplies are either unregulated or regulated. Regulated supplies come in several options including linear, switched and battery-based. A power supply takes the AC from the wall outlet, converts it to unregulated DC, and reduces the voltage using an input power transformer, typically stepping it down to the voltage required by the load.
No single discovery has affected our lives, our culture and our survival more than electricity. Electricity is everywhere; it lights our way, cooks our food and can even brush your teeth. For an example, imagine where the medical field would be without electricity and in that sense how many lives have been saved due to electrical devices like defibrillators, pacemakers, etc. Read on to discover more about basic electrical theory. So what is electricity and where does it come from? More importantly, why is carpet, socks and a doorknob a bad combination? In its simplest terms, electricity is the movement of charge, which is considered by convention to be, from positive to negative.
Electrons in Metals and Semiconductors. R.G. Chambers. 2. Basic Digital Electronics. J.A. Strong. 3. AC and DC Network Theory. A.J. Pointon and H.M. Howarth.
POWER SUPPLY BASICS
At the end of this module you are expected to: 1. Familiarize the characteristics of a sinusoidal waveform, including its general format, average value, and effective value. Discuss and determine the phase relationship between two sinusoidal waveforms of the same frequency. Calculate the average and effective values of any waveform. Direct Current DC as; Current having a single direction unidirectional and a fixed magnitude over time Boylestad,
In elementary school, we learned that everything is made by atoms. This is a product of three particles: Electrons, Protons and Neutrons. As the name suggest Neutron does not have any charge whereas Protons are positive and Electrons are negative.
Фонтейн почти во всем полагался на Стратмора и верил в его план, в том числе и в достойную сожаления, но неизбежную необходимость устранять Энсея Танкадо и в переделку Цифровой крепости, - все это было правильно. Но одно не давало Фонтейну покоя - то, что Стратмор решил прибегнуть к услугам Халохота. Тот, конечно, был мастером своего дела, но наемник остается наемником.
Мы ищем различие, выражаемое простым числом. Через несколько секунд всем стало ясно, что эта затея бессмысленна. Числа были огромными, в ряде случаев не совпадали единицы измерения.
Но не искалеченная рука привлекла внимание Беккера.