Today, if you look around, virtually everything you see is powered by electricity in one form or another.
Alternating current and direct current are the two main forms of charge that power our electrical and electronic world.

What is AC? Alternating current can be defined as a flow of electric charge that changes its direction at regular intervals.

The period / regular intervals at which an AC changes its direction is its frequency (Hz). Marine vehicles, spacecraft, and military equipment sometimes use 400 Hz AC. However, for most of the time, including indoor use, the AC frequency is set to 50 or 60 Hz.

What is DC? (Symbol on electrical appliances) D.C is a current (flow of electric charge or electrons) that flows in only one direction. Subsequently, there is no frequency associated with DC. DC or direct current has zero frequency.
AC and DC sources:

AC: Power plants and alternators produce alternating current.

DC: Solar panels, fuel cells, and thermocouples are the main sources for DC production. But the main source of DC is AC conversion.

AC and DC application:

The AC is used to power refrigerators, home fireplaces, fans, electric motors, air conditioners, televisions, food processors, washing machines, and almost all industrial equipment.

DC is mainly used to power electronics and other digital equipment. Smartphones, tablets, electric cars, etc. LED and LCD TVs also run on DC, which is converted from a normal AC mains.

Why AC is used to transmit electricity. It's cheaper and easier to manufacture. AC at high voltage can be transported hundreds of kilometers without much loss of power. Power plants and transformers reduce the amount of voltage to (110 or 230 V) in order to transmit it to our homes.

What is more dangerous? AC or DC?
It is believed that DC is less dangerous than AC, but there is no definitive proof. There is a misconception that contact with high voltage AC is more dangerous than low voltage DC. Actually, it's not about voltage, it's about the amount of current passing through the human body. Direct and alternating current can be fatal. Do not insert fingers or objects into sockets or gadgets and high power equipment.

Electrical energy accompanies us at every step. Without it, the life of any person is unthinkable. Throughout life, in one way or another, we encounter manifestations of electricity. This happens more densely, as a rule, when electrical appliances break down. And in order to understand their device and circuits, it is useful to know that alternating and direct current are denoted as AC and DC current.

Sources of electrical energy

Initially, only single-use chemical galvanic cells were the only sources of electricity. Subsequently, reusable batteries appeared. It is noteworthy that the polarity of chemical sources is not able to change by itself. In order to obtain a constant voltage Generators are used commercially and sometimes solar panels.

Electronic equipment, in turn, is powered by the mains AC voltage, and power supplies are used to obtain a constant. To the required indicators, the alternating current is reduced by means of transformers and subsequently rectified. In this case, the ripple frequency is reduced by smoothing filters, stabilizers and voltage regulators.

AT modern world common impulse blocks nutrition. In them, the ripple frequency of the output electricity is smoothed out by integrating elements. They concentrate electrical energy and give it to the load. The result is the required constant voltage.

Electrolytic capacitors can also condense electrical energy. When such a capacitor is discharged, an alternating current appears in the external circuit. If it is discharged through a resistor, then a gradually decreasing (unidirectional) alternating current occurs. When using an induction coil, a bidirectional alternating current is generated in the circuit. Electrolytic capacitors can have a huge capacitance reaching hundreds of microfarads. When such capacitors are discharged through a large resistance, electricity decreases more slowly and a constant voltage flows in the external circuit.

There are also combinations of capacitors and chemical sources - ionistors. They have the ability to accumulate and give off a significant amount of electricity. A typical example is electric vehicles.

Designations on diagrams and in devices

It is generally accepted that the direction of electricity goes from the contact with the plus sign to the contact with the minus sign.

Places with high potentials are called the "positive pole" and are indicated by a + (plus) sign. Points with lower potentials, respectively, are called the "negative pole" and are denoted by the sign - (minus).

Initially, it is accepted that the electrical insulation of positive wires is red, while wires with a minus sign are painted blue or black.

Symbols on electrical appliances:- or =. Unidirectional electricity (including permanent) is denoted by the Latin DC, or the Unicode character U+2393 is used.

The abbreviation AC and DC is firmly rooted in everyday life and is used on a par with the usual names "variable" and "constant":

• designation of direct voltage (-) or DC (Direct Current);
• alternating current sign (~) or AC (Alternating Current) - alternating current designation.

Applications of DC voltage

The use of direct voltage allows you to increase the transmitted electrical energy and then transfer it between power systems that use alternating current of different frequencies (for example, 50 and 60 hertz).

Direct current is also actively used in transport. Permanently excited electric motors are used in various mechanisms:

• electric locomotives;
• electric trains;
• trams;
• trolleybuses;
• lifts, etc.

Not without constant tension in other areas of science and technology. It is widely used in this way:

Electricity accompanies us everywhere: at work and at home. It is scary even for a moment to imagine what will happen to humanity if it suddenly loses electrical energy.

Direct, or DC current, is called the flow electric charges, which does not change its direction and strength over time, which, according to the classical definition of this quantity, is measured in coulombs per second (or amperes).

When getting acquainted with electrical phenomena of a permanent nature, it is important to remember not only the direction of the flow of physical processes, but also their intensity (strength). In real life electrical or electronic equipment, the DC value is rarely completely constant.

Causes of Impermanence

The fact is that at the output of any rectifier circuit that converts alternating current, there are always low-frequency harmonics of the original signal, called ripples.

Note! When working with batteries and galvanic cells, it is also not entirely correct to talk about its constancy, since this can only apply to the concept of “polarity”.

The strength of the electron flow in any load also changes (decreases) over time, which is associated with a decrease in the EMF of the power source.

From the above reasoning, it follows that it is possible to speak about the constancy of the current characteristics in these circuits only with a certain degree of conventionality. It is acceptable only in situations where changes in its strength can be neglected.

Main current characteristics

When considering the main parameters of this physical quantity, we immediately make a reservation that the often used term “current strength” is recognized by most experts as not entirely correct. Much more suitable for designating its scalar characteristic is not force, but the speed (sometimes called intensity) of the movement of free electric charges.

According to the classical concept, this speed is defined as the amount of charge moving through a given section of a conducting material per unit time. It is this indicator, taken as a unit of current strength, that is called one Ampere.

Thus, a flow of one Ampere is the movement of a charge of one Coulomb through a given conducting section in a time equal to a second. Another characteristic of direct current, associated with its flow through a load with resistance R, is called voltage drop, which is measured in Volts. It is defined as the potential difference formed on the conductor when one ampere flows through it.

The same definition can be presented in the following form. One Volt is such a potential difference between points spaced apart in an electric field, which is enough to do work of one Joule (when a charge of one Coulomb is transferred between them).

The practical characteristics of the current component obtained by means of rectifiers usually include the following parameters:

• The amplitude of the pulsations, defined as the difference between its limiting values;
• The ripple index, represented as a ratio of two quantities, in which the numerator is AC current, and the denominator is DC.

Let's explore the latter in more detail.

DC component

When studying the shape of the load current at the output of a diode rectifier using an oscilloscope, it is possible to discern its ripples, which manifest themselves due to the limited capabilities of the filtering components (capacitances).

AT individual cases these components are so small that they may not be taken into account when calculating circuits in which filter capacitors should be installed. With this approach to the category, it is more convenient to consider the indicator under study as an impulse or pulsating one and distinguish its two components: DC and ac. Let's look at each of these components in more detail.

Constant DC

The specified value is calculated as the average value of the current action during the period. It is fundamentally different from another characteristic of a pulsating flow, called the variable component ac.

Changing Component

Alternating current (more precisely, the component of the pulsating current) ac is a periodic oscillation of its amplitude around the previously considered average position. When calculating this value, it should be assumed that its value includes the following components:

• permanent part;
• The value of the variable component (ac), defined as the root mean square value.

Both of them are components of the studied current signal and, like all electrical parameters, have a fixed power (that is, the ability to perform a certain work). The latter is calculated as:

where I is the root mean square of the DC component and current ripple.

That is, when calculating the power, the components of the constant DC and the variable ac are summed up as complex quantities.

Additional Information. In this case, they are represented as vector components of the original signal.

It is also important that all the considered definitions, as well as the symbols AC and DC, are equally applicable to the category "voltage".

In conclusion, let us once again pay attention to the fact that the concept of direct current is most often associated with the invariance of the direction of the flow of free electrons. However, in reality, this concept involves taking into account a number of scalar characteristics, one of which is the intensity of the charge flow in a passive load.

With the nominal value of this current component changing in time, it can be considered constant only conditionally, which is allowed within the framework of the problem being solved in each specific case.

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Biography

AC/DC(abbreviated from English alternating current / direct current alternating current / direct current) Australian rock band formed in Sydney (Australia) in November 1973 by brothers Malcolm and Angus Young.

Together with bands like Led Zeppelin, Black Sabbath and Deep Purple AC/DC often regarded as the pioneers of hard rock and heavy metal. The musicians themselves classified their music as rock and roll, since it is based on rhythm and blues with a heavily distorted sound of rhythmic and solo guitars.

The band went through several lineup changes before the band's first album, High Voltage, was released in 1975. The band's line-up remained unchanged until bassist Mark Evans was replaced by Cliff Williams in 1977. Ronald Belford "Bon" Scott died on February 19, 1980, choking on his own vomit as a result of extreme intoxication. The group had every chance to break up, but Scott's replacement was soon found in the person of former Geordie vocalist Brian Johnson. A year later, the band released their best-selling album, Back in Black.

The band has sold over 200 million albums worldwide, including 68 million in the US. The most successful album, Back in Black, sold over 22 million in the US and over 42 million overseas. Generally, AC/DC is the most successful and famous rock band from Australia. AC/DC ranked #4 on VH1's 100 Greatest Artists of Hard Rock and #7 on MTV's Greatest Heavy Metal Band Of All Time.

Name

Malcolm and Angus Young came up with the band's name after seeing the acronym "AC/DC" on the back of a sewing machine owned by their sister Margaret. "AC/DC" is an abbreviation for "alternating current/direct current", which indicates that the device can use the specified types of energy. The brothers felt that the name symbolized the raw energy of the band and the energy of live performances, thus the name stuck.

In some cultures, "AC/DC" is slang for bisexuals; the musicians claimed that they were unaware of the existence of this meaning until a taxi driver noticed this fact early in their career. Some religious figures argue that the name of the group should be understood as "Anti-Christ / Devil's Child" (English "Anti-Christ / Devil"s Child"), "Anti-Christ / Death to Christ" (English "Anti-Christ / Death to Christ" ) or "After Christ/Devil Comes" (eng. "After Christ/Devil Comes").

"AC/DC" is spelled but the group is also known as "Acca Dacca" in Australia. The name led to the emergence of tribute bands using consonant names: BC / DC from British Columbia (Canada); AC/DSHE, a girl group from San Francisco; Swedish AB/CD and some others.

It is known that the group performed several times for the Freeride Entertainment team in films about Mountain Bike, from the Disorder series (in parts 4 and 5, on this moment there are 9 of them)

Story

Brothers Angus (born March 31, 1955; at the request of Atlantic Records, the incorrect 1959 was officially indicated as the year of birth of Angus), Malcolm (born January 6, 1953) and George Young (George Young) were born in Glasgow (Scotland) and still children with their family left for Sydney. George was the first to play guitar and became a member of Australia's most successful band of the 60s, The Easybeats. They were the first local rock band to have an international hit with "Friday on My Mind" in 1966. Malcolm soon followed in his brother's footsteps, becoming the guitarist for the Newcastle band The Velvet Underground (not to be confused with the New York band The Velvet Underground).

Early years

After getting their first musical experience, Malcolm and Angus organized in November 1973 AC/DC, inviting vocalist Dave Evans, bass guitarist Larry van Kniedt and drummer Colin Burgess to the band. The band's debut took place on December 31, 1973 at the Chequers bar in Sydney.

The original line-up changed frequently - the band changed several drummers and bassists during 1974. In September 1974, AC/DC replaced Dave Evans with the charismatic Ronald "Bon" Scott (born July 9, 1946 in Kirrimer, Scotland), lead singer of The Spectors in 1966. From this event began the real success of the group. With Evans, AC/DC recorded a three-song single: "Rockin' in the Parlour", "Show Business" and "Can I Sit Next to You Girl", the latter two were also recorded with Scott.

Angus Young's sister encouraged him to wear the school uniform he wore to Ashfield Boys High School in Sydney. He later wore this uniform at all concerts of the group.

Through continued participation in the popular music television show Countdown, broadcast throughout Australia, between 1974 and 1978 the group became one of the most famous and popular in the country. AC/DC a number of successful albums and singles were released during these years, including the timeless rock 'n' roll anthem "Its a Long Way to the Top (If You Wanna Rock "n" Roll)". -roll]).

worldwide fame

The group signed an international contract with Atlantic Records and began touring extensively in the UK and Europe, gaining fame and gaining experience performing in the wake of well-known rock bands of the time, such as Alice Cooper, Black Sabbath, KISS, Cheap Trick, Nazareth, Foreigner, Thin Lizzy and The Who. 1976 saw the release of AC/DC's third Australian album, Dirty Deeds Done Dirt Cheap.

Invasion and wave of popularity of punk rock 7678. the band survived well thanks to their crude and provocative lyrics and, in part, because they were classified as punk bands in the British music press of the time. They achieved success on the British rock scene with their powerful and controversial live shows, and Angus Young quickly became famous for his provocative stage behavior, which, among other things, led to the group being banned from several UK venues. .

The 1979 album Highway to Hell, produced by Mutt Lange, catapulted the band to the top of the world rock charts of all time. The album was undoubtedly the most popular of the band's discography at the time of release. Many of the songs from this album are still frequently heard on the radio, and the title track has become one of the most famous songs in the history of rock music.

Death of Bon Scott

Bon Scott died on February 19, 1980. He left another party and stayed overnight in the car of his friend Alistair Kinnear (Allistair Kinnear). He found Bon dead the next day. The cause of death was officially hypothermia, although the most common version to this day is that Bon Scott choked on his own vomit. These rumors are supported by many contradictions in the official story of his death, which also gives rise to many theories about a conspiracy, the murder of a musician and a heroin overdose.

The members of the group originally planned to end their musical activities as part of AC/DC, but later decided that Bon Scott would like the band to continue. The musicians tried several candidates for the position of the vocalist, as a result, two contenders remained: Terry Slesser (Terry Slesser) and Brian Johnson (Brian Johnson). Johnson during this period tried to restore his group Geordie, but the performance of two songs in public AC/DC and Tina Turner ("Whole Lotta Rosie" (Let There Be Rock) and "Nutbush City Limits", respectively) impressed the members AC/DC and a few days later they informed Johnson that he was the band's new vocalist.

Back in Black

Together with Brian Johnson, the group completed songs that were not completed due to Bon's death, and recorded the album Back in Black, also produced by Lang. Back in Black, released in 1980, became the band's best-selling album and one of the most significant in the history of hard rock. Among the hits on the album, the song of the same name written in memory of Bon Scott and "You Shook Me All Night Long" are considered by many to be the quintessential music. AC/DC and even hard rock in general.

The next album, For Those About to Rock (We Salute You), released in 1981, also sold very well and was well received by critics. The composition of the same name to the album, ending under the thunder of firing cannons, became the culminating and final number of most subsequent concerts AC/DC.

The 1983 album Flick of the Switch was produced by the band without Lang. Drummer Phil Rudd left the band due to personal disagreements with the rest of the band, caused, according to some sources, by problems with alcohol. In his place, after an anonymous audition, they took Simon Wright, a former member of the band Tytan. In 1985, with the new line-up, the band recorded the less successful Fly on the Wall, produced by the Young brothers. Along with this album, the band released a series of music videos of the band performing five of the album's ten songs in a bar, using various special effects including an animated fly.

In 1986, AC/DC returned to the charts with the title track of Who Made Who, the soundtrack to the Stephen King film Maximum Overdrive. The album also contained two new instrumentals and hits from previous albums. In February 1986, the band was inducted into the Australian Recording Industry Association Hall of Fame. The 1988 album Blow Up Your Video was released by the group along with the original production line-up, Harry Vanda and George Young. This album sold better than the previous one and entered the UK Top 20 Singles Chart with the song "Heatseeker".

After the release of Blow Up Your Video, Wright left the band and was replaced by session musician Chris Slade. Johnson could not participate in the work of the group for several months, so the Young brothers wrote the songs for the next album on their own, as well as for all subsequent ones. The Razor's Edge album was released in 1990. It became very successful for the group and contained the hits "Thunderstruck" and "Money Talks". The album became multi-platinum, entered the top ten of the US charts (2nd place) and twenty singles in Great Britain.

Phil Rudd returned to the band in 1994. Chris Slade's departure, in this regard, was amicable and was mainly due to the strong desire of the members of the group to return Rudd. According to Angus Young, Slade was the best musician in the world. AC/DC, but the desire to see Phil in the group was stronger. As part of the 1980s and 1983s, the band recorded the 1995 album Ballbreaker with hip hop and heavy metal producer Rick Rubin and Stiff Upper Lip in 2000.

After the release of these albums, the band signed a long-term multi-album deal with Sony BMG, which was released under the Epic Records label.

Recent years and recognition

In March 2003, AC/DC was inducted into the New York Rock and Roll Hall of Fame and performed their hits "Highway to Hell" and "You Shook Me All Night Long" with Aerosmith's Steve Tyler. In May 2003, Malcolm Young was awarded the Ted Albert Award for "outstanding contribution to Australian music". That same year, the Recording Industry Association of America (RIAA) updated the group's album sales figures from 46.5 million to 63 million, making AC/DC the fifth highest-selling group in US history behind The Beatles, Led Zeppelin, Pink Floyd and Eagles. In addition, Back in Black was certified double diamond (20,000,000 copies sold), making it the sixth best-selling album in US history. In 2005, the album sold 21 million copies, placing it at number five.

In July 2003, the band performed with The Rolling Stones at Sarsfest, a SARS concert in Toronto, Canada.

On 1 October 2004, Melbourne's Corporation Lane was officially renamed ACDC Lane in honor of the group (street names in Melbourne cannot contain the "/" character). The street is next to Swanston Street, where the band recorded their video for the 1975 hit "Its a Long Way to the Top" in the back of a truck. There is also another street in the world named after the AC / DC group, in Spain, in the city of Legan (LeganГ©s), near Madrid "Calle de AC / DC", not far from the streets named after the rock bands Iron Maiden and Rosendo (Spanish rock band).

In March 2005, a set of two DVD discs, "Family Jewels", containing a music video and clips from concerts. The first disc is from the Bon Scott era (with live footage taken ten days before Scott's death), the second contained footage from the Brian Johnson era.

On August 28, 2008, the single "RocknRoll Train" was released. October 20, 2008 AC / DC released their new album Black Ice, which a week after the release topped the charts in 29 countries around the world. In the first week, the band sold 5 million copies of the album worldwide. Australian Top 50 hit 6 albums in early November AC/DC. Among those who spoke enthusiastically about the new album was the Australian poet and writer John Kinsella, who noted the album's "smart, sharp, in its own way genius" lyrics.

At the end of October, the band went on a tour of North America, inviting The Answer as support acts.

Influence on rock music

AC/DC is mentioned by many contemporaries and later musicians and rock and metal bands as an influence on their work. Among them: Anthrax, Bon Jovi, The Darkness, Def Leppard, Dio, Dokken, Dream Theater, Faster Pussycat, Iron Maiden, Great White, Guns N "Roses, Hanoi Rocks, Journey, Megadeth, Metallica, Nirvana, Mötley Crüe, Ozzy Osbourne, Poison, Ratt, Rhino Bucket, Saxon, Scorpions, Skid Row, Supagroup, Tool, Twisted Sister, UFO, Van Halen, Whitesnake, Wolfmother, Y&T.

Many artists and bands from punk rock, hardcore punk, grunge, garage rock and alternative rock have also noted AC/DC how it influenced them. Although the group was initially criticized by British punk rockers of the late 70s, many musicians of this movement paid tribute to AC/DC for the high energy of music, solid and anti-commercial (although many may argue with this) approach to rock music.

Influence AC/DC on Australian music is difficult to overestimate. Relatively speaking, every Australian rock band that appeared in the mid-70s and later was influenced by AC/DC. To Australian bands who mentioned influence on them AC/DC, include, for example, Airbourne, Blood Duster, Frenzal Rhomb, INXS, Jet, The Living End, Midnight Oil, Powderfinger, Silverchair, You Am I.

Do you know what the words AC (alternating current) and DC (direct current) mean on welding machines and electrodes? In essence, these terms describe the polarity electric current, which is generated by the power source and sent to the workpiece through the electrode. Choosing the correct polarity for a particular brand of electrodes has a significant impact on the strength and quality of connections - so do not forget to check the label on the package! To make sure once again, you can make two trial attempts with different polarity on the edge of the workpiece.

In everyday life, the terms "direct" and "reverse" polarity or "electrode-negative" and "electrode-positive" polarity are used. The latter sounds more illustrative and therefore here we will use exactly these notations.

Polarity is due to the fact that the electrical circuit has a negative and positive poles. Direct current (DC) always moves in the same direction, which is why its polarity is always the same. Alternating current (AC) moves half the time in one direction and half in the other. Thus, at a frequency of 60 Hertz, the polarity of the current changes 120 times per second.

The welder must have a good understanding of what polarity is and how it affects the welding process. With some exceptions, electrode-positive (reverse) polarity provides deeper penetration. Electrode-negative (straight) polarity has a higher electrode melting performance and, as a result, deposition performance. This can be affected by the chemicals in the coating. Cellulosic coated carbon steel electrodes such as Fleetweld 5P or Fleetweld 5P+ are generally recommended for positive polarity. Some types of gas shielded electrodes are suitable for welding with both types of polarity.

The use of transformer-type welding machines has created a need for electrodes suitable for welding with any polarity due to constant changes in the direction of the alternating current. Although alternating current itself has no polarity, if AC welding electrodes are used with direct current, they will show lower results. Therefore, electrode manufacturers usually indicate the most appropriate polarity on the coating and packaging of the electrodes.

To ensure the required penetration, uniform weld shape and high welding performance, the correct polarity must be used. Incorrect polarity will cause poor penetration, inconsistent bead shape, excessive spatter, arc control problems, overheating, and rapid electrode burnout.

Most devices have pins clearly labeled or detailed how to set them to a specific polarity. For example, some devices have a polarity switch, while others require changing the cable connectors. If you are not sure which polarity is currently in use, there are two easy ways to find out. The first is DC carbon welding, which will only work properly with straight polarity. The second is welding with the Fleetweld 5P electrode, which shows much top scores with reverse polarity.

Polarity check:

A: Polarity detection with carbon electrode

2. Sharpen the tips of the two carbon electrodes on the grinding wheel so that they have the same shape in a smooth bevel starting 5–7.5 cm from the tip of the electrode.
3. Insert one electrode into the electrode holder near the start of the bevel.
4. Set the welding current to 135-150A.
5. Select the polarity you are interested in.
6. Light the arc (don't forget the mask) and wait a while. Increase the length of the arc to make it easier to observe the action of the arc.
7. Observe the arc. With electrode-negative (straight) polarity, the arc has a conical shape and is highly stable, easy to control and uniform.
With electrode-positive (reverse) polarity, the arc is quite difficult to control. It will leave black deposits of carbon on the base metal.
8. Reverse polarity. Ignite the arc with the second electrode and wait the same time. Watch the arc.
9. Compare the tips of the two electrodes. With direct polarity, the electrode burns evenly, retaining its shape. With reverse polarity, the electrode quickly burns out and takes a flat shape.

B. Polarity detection with metal electrode (E6010)

1. Clean the base metal and place it horizontally.
2. Set the welding current to 130-145 A (for electrodes with a diameter of 4 mm).
3. Select one of the polarities.
4. Light the arc. Start welding using the standard arc length and electrode angle.
5. Listen for the sound of the arc. With proper polarity, normal arc length and current strength, the arc will produce a uniform "crackle".
Incorrect polarity at normal arc length and current will cause irregular "crunching" and "popping" and arc instability. See above how the arc behaves and how the weld looks when using a metal electrode with correct and incorrect polarity.
7. Reverse polarity and create a second seam.
8. Clean the seams and inspect them carefully. With incorrect, straight polarity, the seam will have the negative characteristics listed in Lesson 1.6.
9. Repeat several times until you can quickly determine the current polarity.