Mempelajari tenaga listrik bagi sebagian orang memang perlu terutama bagi mahasiswa pendidikan teknik listri / elektro. teknik-teknik dalam bidang ketenagaan merupakan dsar untuk menjadi teknisi yang handal dan kompeten. kali ini saya akan berbagi sedikit teknik transmisi tenaga listrik. dokumen dapat di download di bawah ini :
http://www.ziddu.com/download/9669087/Teknik_transmisi_tenaga_listrik_jilid_1.zip.html
http://www.ziddu.com/download/9669086/Teknik_transmisi_tenaga_listrik_jilid_2.zip.html
Read More..
Tampilkan postingan dengan label electrical. Tampilkan semua postingan
Tampilkan postingan dengan label electrical. Tampilkan semua postingan
Jumat, 30 April 2010
With Google Adsense earnings, the possibilities are limitless
With Google Adsense earnings, the possibilities are limitless. Yet there is also the possibility of someone taking advantage of the easy money process that this internet marketing is doing. If you think more about it, these negative factors may force Google to break down and thrash Adsense in the process. If that happens, people would have to go back to the old ways of internet marketing that does not make money online as easy as Adsense earnings.
For now, however, Google Adsense earnings are here to stay. As long as there are people wanting to earn some easy cash online just using their talents, the future ahead is looking good. For more results log on to www.thegoogleincome.com. Besides with all the strict guidelines that Google is enforcing over Adsense earnings, it will take awhile for the Adsense privileges to be spammed and even terminated.
For the last couple of years, Google Adsense has taken control of forums, discussions and newsletters all over the Internet. Already, there are tales of fabulous money to be made and millions made by those who are working from home. It seems that Google Adsense earnings have already dominated the internet marketing business and is now seems to be the easiest way to making money online.
The key to success with Google Adsense earnings is the placing of ads on pages that are receiving high traffic for high demand keywords. The higher the cost-per-click to the advertiser, the more you will receive per click from your website. Obviously, it does not pay to target low cost-per-click keywords and place them on pages that do not receive hits.
With all the people getting online and clicking away everyday, it is no wonder why Google Adsense earnings have become an instant hit.
For some who are just new to this, it would be a blow to their pride knowing that their homepage is buried somewhere in the little ads promoting other people’s services. But then, when they get the idea that they are actually earning more money that way, all doubts is laid to rest.
There are two major, and clever, factors that some successful webmaster and publishers are learning to blend together in order to make money easier using Adsense.
1. Placing Adsense links on pages that are producing little, or better yet, no profit. By placing Adsense on a free resources page, you will reduce the amount of potential customers being lost to other sites. Tricky, but effective nonetheless.
2. Targeting high traffic pages on your website. If you check on your logs, you will discover that many of your visitors are taking advantage of the free affiliate marketing resources and ebooks that you are offering on your site. In simple words, your ads are working effectively and are generating more clicks. It also means more money for you.
When learned to work effectively, these two factors are actually a good source of producing a minimal amount of revenue from a high traffic page. Many people are using this strategy to pick up some extra and cash with Adsense earnings. This is also especially rewarding to informational sites that focus their efforts on delivering powerful affiliate link free content to their visitors. Now they can gain a monetary return on their services.
The possibility of adding is 2nd tier in Adsense earnings is not impossible. With all the people spending more time in their Adsense now and still more getting into this line of marketing, there is no doubt about the many new improvements yet to be made. You can also go to www.google-atm-machine.com. Imagine the smiles on the faces of the webmasters and publishers all around the world if ever they sign up for sub-affiliates and double or even triple the amount that they are already earning.
The one particularly handy money-making feature that is available with Adsense now is the ability to filter out up to 200 urls. These gives webmasters the option to block out low value offers from their pages as well as competitors to their websites. Talk about taking only those that are advantageous and discarding the ones that seem “useless”.
With the many techniques that people are now learning on how to make the easiest money by their Adsense, it is not surprising that Google is trying everything to update and polish their Adsense in order to maintain their good image.
sumber: kiosadsense
Read More..
For now, however, Google Adsense earnings are here to stay. As long as there are people wanting to earn some easy cash online just using their talents, the future ahead is looking good. For more results log on to www.thegoogleincome.com. Besides with all the strict guidelines that Google is enforcing over Adsense earnings, it will take awhile for the Adsense privileges to be spammed and even terminated.
For the last couple of years, Google Adsense has taken control of forums, discussions and newsletters all over the Internet. Already, there are tales of fabulous money to be made and millions made by those who are working from home. It seems that Google Adsense earnings have already dominated the internet marketing business and is now seems to be the easiest way to making money online.
The key to success with Google Adsense earnings is the placing of ads on pages that are receiving high traffic for high demand keywords. The higher the cost-per-click to the advertiser, the more you will receive per click from your website. Obviously, it does not pay to target low cost-per-click keywords and place them on pages that do not receive hits.
With all the people getting online and clicking away everyday, it is no wonder why Google Adsense earnings have become an instant hit.
For some who are just new to this, it would be a blow to their pride knowing that their homepage is buried somewhere in the little ads promoting other people’s services. But then, when they get the idea that they are actually earning more money that way, all doubts is laid to rest.
There are two major, and clever, factors that some successful webmaster and publishers are learning to blend together in order to make money easier using Adsense.
1. Placing Adsense links on pages that are producing little, or better yet, no profit. By placing Adsense on a free resources page, you will reduce the amount of potential customers being lost to other sites. Tricky, but effective nonetheless.
2. Targeting high traffic pages on your website. If you check on your logs, you will discover that many of your visitors are taking advantage of the free affiliate marketing resources and ebooks that you are offering on your site. In simple words, your ads are working effectively and are generating more clicks. It also means more money for you.
When learned to work effectively, these two factors are actually a good source of producing a minimal amount of revenue from a high traffic page. Many people are using this strategy to pick up some extra and cash with Adsense earnings. This is also especially rewarding to informational sites that focus their efforts on delivering powerful affiliate link free content to their visitors. Now they can gain a monetary return on their services.
The possibility of adding is 2nd tier in Adsense earnings is not impossible. With all the people spending more time in their Adsense now and still more getting into this line of marketing, there is no doubt about the many new improvements yet to be made. You can also go to www.google-atm-machine.com. Imagine the smiles on the faces of the webmasters and publishers all around the world if ever they sign up for sub-affiliates and double or even triple the amount that they are already earning.
The one particularly handy money-making feature that is available with Adsense now is the ability to filter out up to 200 urls. These gives webmasters the option to block out low value offers from their pages as well as competitors to their websites. Talk about taking only those that are advantageous and discarding the ones that seem “useless”.
With the many techniques that people are now learning on how to make the easiest money by their Adsense, it is not surprising that Google is trying everything to update and polish their Adsense in order to maintain their good image.
sumber: kiosadsense
Read More..
Kamis, 04 Maret 2010
SETENGAH-DIKENDALIKAN-FASE TIGA JEMBATAN RECTIFIER
Halaman ini menjelaskan pengoperasian tiga fase semi-penyearah terkendali. Ketika semi-dikendalikan penyearah digunakan, output dari jembatan dikendalikan ketika itu tetap positif. Jika itu cenderung menjadi negatif, output dijepit dengan nol volt melalui tindakan mendorong bebas dari dioda.
Gambar. 1
Rangkaian semi-jembatan penyearah terkendali ditunjukkan pada Gambar. 1, dan sirkuit ini mengandung tiga-SCRs dan tiga dioda. Hal ini mungkin untuk mengkonfigurasi rangkaian pada dua cara. Sebagai contoh, top-setengah dapat berisi dioda dan setengah bagian bawah SCRs. Sebagai alternatif, enam SCRs dapat digunakan seperti dalam kasus jembatan yang dikontrol sepenuhnya rectifier dan dioda tambahan dapat dihubungkan dari rel negatif ke rel positif jembatan, dengan anoda terhubung ke rel negatif dan katoda ke rel positif. Operasi dari sirkuit ini berbeda dari rangkaian yang ditampilkan di atas.
CIRCUIT OPERASI
Pengoperasian dikontrol semi-rangkaian penyearah ditampilkan pada Gambar. 1 sekarang menjelaskan. Gelombang dari tegangan keluaran jembatan untuk menembak sudut 30o ditunjukkan pada Gambar. 2. . Hal ini dapat dilihat bahwa jejak rel positif tegangan output adalah bahwa dari penyearah terkontrol, karena hanya bagian atas setengah dari jembatan dikendalikan. Jejak rel bawah adalah bahwa dari sebuah jembatan penyearah tak terkendali, karena bagian bawah hanya berisi dioda.
Gambar. 2
Biarkan pasokan 3-fase dapat didefinisikan seperti yang ditunjukkan dalam persamaan (1).
Mengingat bahwa sudut tembak adalah 30 o, SCR S 1 adalah terpicu ketika wt = 60 o. Konduksi jangkauan SCRs di bagian atas sekarang dapat dinyatakan dalam persamaan (2).
Selama tembakan sudut a tetap kurang dari 60 o, istilah untuk tegangan keluaran lebih dari satu output siklus dapat dinyatakan sebagai berikut.
Substitusi v R, v Y, dan v B dari persamaan (1), kita mendapatkan bahwa
Substitusi v R, dan v B dari persamaan (1), kita mendapatkan bahwa
Tergantung pada sudut tembak, jembatan output berulang setiap 120 o. Applet ditunjukkan di bawah ini plot tegangan keluaran, mengingat sudut tembak. Diasumsikan bahwa konduksi melalui impedansi beban kontinu.
Read More..HALF-WAVE RECTIFIER DIKENDALIKAN DENGAN RANGKAIAN RL AN LOAD
Pengoperasian rangkaian RL disediakan oleh setengah gelombang penyearah dikendalikan diilustrasikan dalam program ini. Biarkan vs (t) didefinisikan E * sin (wt). Pada wt = 0, arus melalui rangkaian adalah nol. Sebagai wt menjadi> 0, vs menjadi positif. Jika dioda bukan sebuah SCR telah digunakan, dioda akan mulai konduksi pada wt = 0. Dengan SCR, konduksi tidak dimulai sampai SCR terpicu. Biarkan SCR dipicu ketika wt = a. Maka disebut tembak SCR sudut dan terus melakukan.
Ketika wt = p, sumber menjadi nol, tetapi pada saat tersebut, arus melalui rangkaian adalah nol dan tidak ada energi yang tersimpan dalam induktor. Ketika vs menjadi negatif, arus melalui rangkaian tidak akan menjadi nol tiba-tiba karena induktor. Induktor bertindak sebagai sumber dan menjaga SCR maju-bias sampai energi yang tersimpan dalam induktor menjadi nol. Biarkan arus melalui rangkaian menjadi nol pada wt = b dan nilai b> p. Untuk b
Tegangan pada SCR adalah nol ketika aku n> 0. Kalau tidak, itu adalah sama dengan tegangan yang diberikan. Perhatikan bahwa ketika wt
Selanjutnya nilai rata-rata arus beban ditemukan keluar. Arus beban RMS dievaluasi setelah itu.
A = 6,222 Amp d = 3,936 rad
extinction_angle = 225,489 deg
Kepunahan sudut dihitung menjadi 225,49 o.
Curavg = 8,339 Amp
CurRMS = 12,851 Amp
Tegangan pada SCR
Plot Tegangan Output
Vout n: = if (n> 0,001, E. Sin (q n), 0,0)
Read More..
Kamis, 25 Februari 2010
Pengenalan Listrik dan Rangkaian Listrik
The Atom
On the left is a conceptual drawing of an atom. Atoms are the building blocks of matter. Everything is made of atoms, from rocks, to trees, to stars, to even yourself. An atom consists of a tightly packed nucleus containing one or more protons (colored red in the picture), and usually an equal number of neutrons (gray). Electrons (blue) surround the nucleus, forming an electron cloud. The number of electrons in an electrically stable atom is always equal to the number of protons in the nucleus.
Electric Charge
Let's say we steal an electron from one atom and give the electron to another atom. One atom will have an overall positive charge and the other will have an overall negative charge. When this happens, the two atoms are called ions. Because ions have an overall electric charge, they can interact with other charged objects. Since like charges repel and opposite charges attract, a positive ion will attract negatively charged objects, such as electrons or other ions, and will repel positively charged objects. A negatively charged ion will attract positively charged objects, and will repel other negatively charged objects.
The same is true for larger objects. If you take electrons from one object and place them on another object, the first object will have an overall positive charge while the second will have an overall negative charge. Depending on the types of objects and the amount of charge involved, the electric force may be enough to cause the objects to stick together. This phenomenon is often referred to as "static electricity."
The amount of overall electric charge possessed by an object is measured in coulombs. One coulomb is roughly equal to the amount of charge possessed by 6,000,000,000,000,000,000 (six billion billion) electrons. While this may seem like a huge number at first, it is not really that much, since electrons are so tiny. Just to give you an idea, one coulomb is roughly the amount of charge that flows through a 12-watt automotive light bulb in one second.
If the amount of charge possessed by two objects and the distance between them are known, it is possible to calculate the amount of force between the objects using a formula known as Coulomb's law. This law was discovered by Charles Augustin de Coulomb in 1784, and states that the force between two charged objects varies directly as the charges of the objects and inversely as the square of the distance between them. Coulomb's law is given below in formula form:
F is the force, in Newtons.
q and q' are the charges of the two objects, in coulombs.
Whenever electrons are taken from one object and placed on another object, causing an imbalance of charge, we say that a voltage exists. That is what somebody means when they say that something has so many volts of electricity. They are describing a difference of charge in two different places. A standard AA battery has a difference of 1.5 volts between its positive and negative terminal, while car battery has a difference of 12 volts between its two terminals, and the everyday type of static electricity that causes things to stick together and occasionally gives you a jolt when you touch a metal object is usually measured in thousands of volts.
Another way to understand voltage is to think of an "electric field." Imagine a plate with positive charge next to a plate with negative charge. If I place a positive charge between these plates, the plates’ electric field will attract the charge to the negative side. Imagine that I place a 1 coulomb positive charge next to the negative plate, and then pull it towards the positive plate. Because the electric field creates a force in the opposite direction, moving the charge requires energy. The amount of energy depends on the distance between the plates and the strength of the electric field created by the plates. We call this energy the electric field’s "voltage." One volt is the amount of energy in joules required to move 1 coulomb of charge through an electric field. Mathematically, 1Volt = 1Joule / 1Coulomb.
Volts are useful, because they neatly describe the size and strength of any electric field. Visualizing the electric field between two simple plates is easy, but visualizing the field in a complicated circuit with batteries, motors, light bulbs, and switches is very difficult. Voltage simplifies circuits like these by describing the entire electric field with a single number.
Electric Current
The word current comes from the Latin word currere, which means to run or to flow. An electric current is nothing more than the flow of electric charges. Electric charges can only flow through certain materials, called conductors. Although the electrons in most materials are confined to fixed orbits, some materials, including most metals, have many loose electrons which are free to wander around through the material. Materials with this property act as conductors. When a conductor is placed between two charged objects, these loose electrons are pushed away by the negatively charged object and are sucked into the positively charged object. The result is that there is a flow of charge, called a current, and the two object's charges become balanced. The amount of current flowing through a conductor at any given time in measured in amperes, or amps for short. When you read that something uses so many amps, what you are being told is the amount of current flowing through the device. One ampere is equal to the flow of one coulomb of charge in one second.
Batteries and Current
In the previous paragraph, we looked at how current flows from one charged object to another, canceling out the charges of the two objects. Once the charges were canceled, the current stopped. If current were always this short-lived, it would be very impractical. Imagine a flashlight that only lasted a fraction of a second before needing to be recharged! While current does tend to cancel out charges on two objects and then stop flowing, if a charge can be placed on the objects faster than the current can drain the charge, it is possible to keep a current flowing indefinitely. That is what happens in a battery. Chemical reactions within the battery pump electrons from the positive terminal to the negative terminal faster than the device connected to the battery can drain them. The battery will continue to supply as much current as the device requires until the chemicals within the battery are used up, at which point the battery is dead and must be replaced.
Resistance
All conductors offer some degree of resistance to the flow of electric current. What happens is this: As electrons travel through the conductor, they bump into atoms, losing some of their movement in jiggling the atom. The result is that the current flowing through the conductor is slowed down, and the conductor is heated. The amount that a given conductor resists the flow of electric current is measured in ohms.
Power
Whenever current flows, work is done. A conductor may be heated, a motor may be spun, a bulb might give off light, or some other form of energy may be released. There is a simple law that tells exactly how much work may be done by a flowing current. The amount of work done is equal to the voltage of the supply times the current flowing through the wire. This law is expressed in the form P=IV, where P is the power in watts, I is the current in amps, and V is the voltage in volts. For example, if we find that a light bulb draws half of an amp at 120 volts, we simply multiply the 120 volts by half an amp to find that the bulb draws 60 watts of power.
Ohm's Law
Let's say you have a six volt battery and you need to draw two amps of current. What resistance should you make the conductor? Or let's say you have a three volt power supply and a thousand ohm resistor. How much current would flow through the resistor if you were to connect the resistor to the power supply? In order to find the answers to these questions, all you need to do is to use a simple mathematical formula called ohm's law. Ohm's law states that the amount of current flowing through a conductor times the resistance of the conductor is equal to voltage of the power supply. This law is often expressed in the form V=IR, where V is the voltage measured in volts, I is the current measured in amps, and R is the resistance measured in ohms.
electric circuit, unbroken path along which an electric current exists or is intended or able to flow. A simple circuit might consist of an electric cell (the power source), two conducting wires (one end of each being attached to each terminal of the cell), and a small lamp (the load) to which the free ends of the wires leading from the cell are attached. When the connections are made properly, current flows, the circuit is said to be “closed,” and the lamp will light. The current flows from the cell along one wire to the lamp, through the lamp, and along the other wire back to the cell. When the wires are disconnected, the circuit is said to be “open” or “broken.” In practice, circuits are opened by such devices as switches, fuses, and circuit breakers (see fuse, electric; circuit breaker; short circuit). Two general circuit classifications are series and parallel. The elements of a series circuit are connected end to end; the same current flows through its parts one after another. The elements of a parallel circuit are connected so that each component has the same voltage across its terminals; the current flow is divided among its parts. When two circuit elements are connected in series, their effective resistance (impedance if the circuit is being fed alternating current) is equal to the sum of the separate resistances; the current is the same in each component throughout the circuit. When circuit elements are connected in parallel, the total resistance is less than that of the element having the least resistance, and the total current is equal to the sum of the currents in the individual branches. A battery-powered circuit is an example of a direct-current circuit; the voltages and currents are constant in magnitude and do not vary with time. In alternating-current circuits, the voltage and current periodically reverse direction with time. A standard electrical outlet supplies alternating current. Lighting circuits and electrical machinery use alternating current circuits. Many other devices, including computers, stereo systems, and television sets, must first convert the alternating current to direct current. That is done by a special internal circuit usually called a power supply. A digital circuit is a special kind of electronic circuit used in computers and many other devices. Magnetic circuits are analogous to electric circuits, where magnetic materials are regarded as conductors of magnetic flux. Magnetic circuits can be part of an electric circuit; a transformer is an example. Equivalent circuits are used in circuit analysis as a modeling tool; a simple circuit made up of a resistor, and an inductor might be used to electrically represent a loudspeaker. Electrical circuits can also be used in other fields of studies. In the study of heat flow, for example, a resistor is used to represent thermal insulation. Operating electric circuits can be used for general problem solving (as in an analog computer). Read More..
On the left is a conceptual drawing of an atom. Atoms are the building blocks of matter. Everything is made of atoms, from rocks, to trees, to stars, to even yourself. An atom consists of a tightly packed nucleus containing one or more protons (colored red in the picture), and usually an equal number of neutrons (gray). Electrons (blue) surround the nucleus, forming an electron cloud. The number of electrons in an electrically stable atom is always equal to the number of protons in the nucleus.
Electric Charge
A curious thing happens between protons and electrons: a proton and an electron are always attracted to one another, while a proton will repel other protons, and an electron will repel other electrons. This behavior is caused by something called the electric force. Protons are said to have a positive electric charge, while electrons have a negative electric charge. Two objects with the same type of charge push away from each other, while two objects with opposite charges attract to each other. Since a proton and an electron have opposite electric charges, they are attracted to each other. Two protons, however, move away from each other because of their equal electric charges. The same is true of two electrons, which push away from each other because of their equal negative charges.
Most matter contains an equal number of protons and electrons. The negative electrons balance out the positive protons, and the matter has no overall electrical charge. The word overall is important, since the charges are still there, bouncing around inside the matter. Electrical charges are everywhere, but we just can't sense them because they are in balance. In fact, if you take chemistry, you'll learn that the electric force is the very thing that holds matter together. The next time you pick something up, just think that whatever you are holding is literally filled with electric charge. This is an important fact that many people miss when they study electricity.
Let's say we steal an electron from one atom and give the electron to another atom. One atom will have an overall positive charge and the other will have an overall negative charge. When this happens, the two atoms are called ions. Because ions have an overall electric charge, they can interact with other charged objects. Since like charges repel and opposite charges attract, a positive ion will attract negatively charged objects, such as electrons or other ions, and will repel positively charged objects. A negatively charged ion will attract positively charged objects, and will repel other negatively charged objects.
The same is true for larger objects. If you take electrons from one object and place them on another object, the first object will have an overall positive charge while the second will have an overall negative charge. Depending on the types of objects and the amount of charge involved, the electric force may be enough to cause the objects to stick together. This phenomenon is often referred to as "static electricity."
There are several ways to steal electrons from one object and give them to another. Some of the ways include chemical reactions, mechanical motion, light, and even heat. If you rub a glass rod with silk, the electrons in the glass rod will be knocked off and collected on the silk. The glass rod gains an overall positive charge, and the silk gains an overall negative charge. In a battery, chemical reactions are used to force electrons from the positive terminal and place them on the negative terminal.
The amount of overall electric charge possessed by an object is measured in coulombs. One coulomb is roughly equal to the amount of charge possessed by 6,000,000,000,000,000,000 (six billion billion) electrons. While this may seem like a huge number at first, it is not really that much, since electrons are so tiny. Just to give you an idea, one coulomb is roughly the amount of charge that flows through a 12-watt automotive light bulb in one second.
If the amount of charge possessed by two objects and the distance between them are known, it is possible to calculate the amount of force between the objects using a formula known as Coulomb's law. This law was discovered by Charles Augustin de Coulomb in 1784, and states that the force between two charged objects varies directly as the charges of the objects and inversely as the square of the distance between them. Coulomb's law is given below in formula form:
F is the force, in Newtons.
q and q' are the charges of the two objects, in coulombs.
r is the distance between the objects, in meters.
k is a constant equal to 8.98755×109 N m2 C-2
Whenever electrons are taken from one object and placed on another object, causing an imbalance of charge, we say that a voltage exists. That is what somebody means when they say that something has so many volts of electricity. They are describing a difference of charge in two different places. A standard AA battery has a difference of 1.5 volts between its positive and negative terminal, while car battery has a difference of 12 volts between its two terminals, and the everyday type of static electricity that causes things to stick together and occasionally gives you a jolt when you touch a metal object is usually measured in thousands of volts.
Another way to understand voltage is to think of an "electric field." Imagine a plate with positive charge next to a plate with negative charge. If I place a positive charge between these plates, the plates’ electric field will attract the charge to the negative side. Imagine that I place a 1 coulomb positive charge next to the negative plate, and then pull it towards the positive plate. Because the electric field creates a force in the opposite direction, moving the charge requires energy. The amount of energy depends on the distance between the plates and the strength of the electric field created by the plates. We call this energy the electric field’s "voltage." One volt is the amount of energy in joules required to move 1 coulomb of charge through an electric field. Mathematically, 1Volt = 1Joule / 1Coulomb.
Volts are useful, because they neatly describe the size and strength of any electric field. Visualizing the electric field between two simple plates is easy, but visualizing the field in a complicated circuit with batteries, motors, light bulbs, and switches is very difficult. Voltage simplifies circuits like these by describing the entire electric field with a single number.
Electric Current
The word current comes from the Latin word currere, which means to run or to flow. An electric current is nothing more than the flow of electric charges. Electric charges can only flow through certain materials, called conductors. Although the electrons in most materials are confined to fixed orbits, some materials, including most metals, have many loose electrons which are free to wander around through the material. Materials with this property act as conductors. When a conductor is placed between two charged objects, these loose electrons are pushed away by the negatively charged object and are sucked into the positively charged object. The result is that there is a flow of charge, called a current, and the two object's charges become balanced. The amount of current flowing through a conductor at any given time in measured in amperes, or amps for short. When you read that something uses so many amps, what you are being told is the amount of current flowing through the device. One ampere is equal to the flow of one coulomb of charge in one second.
Batteries and Current
In the previous paragraph, we looked at how current flows from one charged object to another, canceling out the charges of the two objects. Once the charges were canceled, the current stopped. If current were always this short-lived, it would be very impractical. Imagine a flashlight that only lasted a fraction of a second before needing to be recharged! While current does tend to cancel out charges on two objects and then stop flowing, if a charge can be placed on the objects faster than the current can drain the charge, it is possible to keep a current flowing indefinitely. That is what happens in a battery. Chemical reactions within the battery pump electrons from the positive terminal to the negative terminal faster than the device connected to the battery can drain them. The battery will continue to supply as much current as the device requires until the chemicals within the battery are used up, at which point the battery is dead and must be replaced.
Resistance
All conductors offer some degree of resistance to the flow of electric current. What happens is this: As electrons travel through the conductor, they bump into atoms, losing some of their movement in jiggling the atom. The result is that the current flowing through the conductor is slowed down, and the conductor is heated. The amount that a given conductor resists the flow of electric current is measured in ohms.
Power
Whenever current flows, work is done. A conductor may be heated, a motor may be spun, a bulb might give off light, or some other form of energy may be released. There is a simple law that tells exactly how much work may be done by a flowing current. The amount of work done is equal to the voltage of the supply times the current flowing through the wire. This law is expressed in the form P=IV, where P is the power in watts, I is the current in amps, and V is the voltage in volts. For example, if we find that a light bulb draws half of an amp at 120 volts, we simply multiply the 120 volts by half an amp to find that the bulb draws 60 watts of power.
Ohm's Law
Let's say you have a six volt battery and you need to draw two amps of current. What resistance should you make the conductor? Or let's say you have a three volt power supply and a thousand ohm resistor. How much current would flow through the resistor if you were to connect the resistor to the power supply? In order to find the answers to these questions, all you need to do is to use a simple mathematical formula called ohm's law. Ohm's law states that the amount of current flowing through a conductor times the resistance of the conductor is equal to voltage of the power supply. This law is often expressed in the form V=IR, where V is the voltage measured in volts, I is the current measured in amps, and R is the resistance measured in ohms.
electric circuit, unbroken path along which an electric current exists or is intended or able to flow. A simple circuit might consist of an electric cell (the power source), two conducting wires (one end of each being attached to each terminal of the cell), and a small lamp (the load) to which the free ends of the wires leading from the cell are attached. When the connections are made properly, current flows, the circuit is said to be “closed,” and the lamp will light. The current flows from the cell along one wire to the lamp, through the lamp, and along the other wire back to the cell. When the wires are disconnected, the circuit is said to be “open” or “broken.” In practice, circuits are opened by such devices as switches, fuses, and circuit breakers (see fuse, electric; circuit breaker; short circuit). Two general circuit classifications are series and parallel. The elements of a series circuit are connected end to end; the same current flows through its parts one after another. The elements of a parallel circuit are connected so that each component has the same voltage across its terminals; the current flow is divided among its parts. When two circuit elements are connected in series, their effective resistance (impedance if the circuit is being fed alternating current) is equal to the sum of the separate resistances; the current is the same in each component throughout the circuit. When circuit elements are connected in parallel, the total resistance is less than that of the element having the least resistance, and the total current is equal to the sum of the currents in the individual branches. A battery-powered circuit is an example of a direct-current circuit; the voltages and currents are constant in magnitude and do not vary with time. In alternating-current circuits, the voltage and current periodically reverse direction with time. A standard electrical outlet supplies alternating current. Lighting circuits and electrical machinery use alternating current circuits. Many other devices, including computers, stereo systems, and television sets, must first convert the alternating current to direct current. That is done by a special internal circuit usually called a power supply. A digital circuit is a special kind of electronic circuit used in computers and many other devices. Magnetic circuits are analogous to electric circuits, where magnetic materials are regarded as conductors of magnetic flux. Magnetic circuits can be part of an electric circuit; a transformer is an example. Equivalent circuits are used in circuit analysis as a modeling tool; a simple circuit made up of a resistor, and an inductor might be used to electrically represent a loudspeaker. Electrical circuits can also be used in other fields of studies. In the study of heat flow, for example, a resistor is used to represent thermal insulation. Operating electric circuits can be used for general problem solving (as in an analog computer). Read More..
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