shock value
Basic electrical device concepts
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Electrical Pathways
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battery polarity
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concepts of voltage levels
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parallel vs. series wiring of components
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schematics
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use of a compass to determine directions/ poles of a magnet
A compass needle points to the magnetic north pole. Earth has two different sets of poles the goegraphic and the magnetic pole
Resistance
A resistor is just a piece of metal, and the piece in the center there is what provides the resistance. And as for what resistance is itself - it is the force against the flow of the electrons. They transform the electrical energy they absorb into heat energy. Imagine our electrons - flowing along the wire, pushing new electrons to flow on, and so on. This wire is not very hard to flow in - it's made of a material that's very conductive. But what would happen if we placed something in the middle of the wire that was harder for the electrons to flow through? They're going to be bumping into all the atoms in the material, which will cause the atoms to vibrate. This, in turn, will cause nearby air molecules to take some energy. That energy is in the form of heat. Where did it come from again? From the electrons bumping into atoms inside the resistor.
Volts
A single volt is defined as the difference in electric potential between two points of a conducting wire when an electric current of one ampere dissipates one watt of power between those points.[2] It is also equal to the potential difference between two parallel, infinite planes spaced 1 meter apart that create an electric field of 1 newton per coulomb. Additionally, it is the potential difference between two points that will impart one joule of energy per coulomb of charge that passes through it. It can be expressed in terms of SI base units ( m, kg, s, and A) as: \mbox{V} = \dfrac{\mbox{kg} \cdot \mbox{m}^2}{\mbox{A} \cdot \mbox{s}^{3}}. It can also be expressed as amps×ohms (Ohm's law), power per unit current (Joule's law), or energy per unit charge: \text{V} = \text{A} \cdot \Omega= \dfrac{\text{W}}{\text{A}} = \dfrac{\text{J}}{\text{C}}. Josephson junction definition[edit] Between 1990 and 1997, the volt was calibrated using the Josephson effect for exact voltage-to-frequency conversion, combined with cesium-133 time reference, as decided by the 18th General Conference on Weights and Measures. The following value for the Josephson constant is used: K{J-90} = 2e/h = 0.4835979 GHz/µV, where e is the elementary charge and h is the Planck constant. This is typically used with an array of several thousand or tens of thousands of junctions, excited by microwave signals between 10 and 80 GHz (depending on the array design).[3] Empirically, several experiments have shown that the method is independent of device design, material, measurement setup, etc., and no correction terms are required in a practical implementation.[4]
Amperes
Amperes(Symbol I or rarely A) To consider Amps pretend that you are the coach of a baseball team. You want to make your team the best that it can be. There are two ways you can do this, making your team score as much as possible and making the opposing team score as little as possible. Focusing on both would be impossible so naturally you're going to have to choose one area to focus on: say you want to score more runs; let's relate this to the concept of "amperes." The amount of runs you make is your score - the more you get the better your chance of winning. Similarly, amperes measure the amount of current you have flowing per second through an area: is it a lot, or a little bit? Now, if you want to win the game, you don't necessarily have to score a whole lot of runs, you just need to score more than your opponent. So, maybe your resistance to their scoring of runs will be high - and resistance to current flowing is also one of our important terms we need to know. Now, how do these concepts of amperes and resistance relate, straying from the daemons for now? If you multiply the resistance by the amperes, you have the voltage of a circuit (remember, we're always talking about in circuits here, not on a baseball field). This relationship was discovered by Georg Simon Ohm, and it says, simply, that: V = I \times R Or Voltage = Current times Resistance Sometimes E is used in place of V, for electromotive force(EMF)
Amperes2
Ampère's force law[7][8] states that there is an attractive or repulsive force between two parallel wires carrying an electric current. This force is used in the formal definition of the ampere, which states that it is "the constant current that will produce an attractive force of 2 × 10-7 newton per metre of length between two straight, parallel conductors of infinite length and negligible circular cross section placed one metre apart in a vacuum".[2][9] The SI unit of charge, the coulomb, "is the quantity of electricity carried in 1 second by a current of 1 ampere".[10] Conversely, a current of one Ampere is one coulomb of charge going past a given point per second: \rm 1\ A=1\tfrac C s. In general, charge Q is determined by steady current I flowing for a time t as Q = It.
battery polarity
Battery polarity is two poles or posts of the battery. The positive pole is usually marked POS, P, or + and is larger than the negative pole which is usually marked NEG, N, or -. The battery and the charger must always match to avoid damage to both.
basic DC circuit theory
Current Flow and Direction "Conventional Current Flow" vs. "Electron Flow" - This has to do with how circuit diagrams are interpreted. Electrons are 'flowing' in the wires. The question here deals with : Do they 'flow' from the positive end of the battery, or the negative end of the battery? Just as where in mathematics subtracting a negative is equivalent to adding a negative, so also a flow of positive charges in one direction is the exact same current as a flow of negative charges in the opposite direction. As such in most applications, the choice of current direction is an arbitrary convention. Conventional current flow, devised by Benjamin Franklin, views the current as a "flow" of positive charges. Therefore, this concept holds that current "flows" out of the positive end of the battery. Electron flow, on the other hand, deals with the ACTUAL route of the electrons (the primary carrier of electric charge in most circuits). Being negatively charged particles, electron currents moves out of the negative end of the battery. Current What is an "electron?" To put it simply, an electron is an atomic particle which carries a negative charge. These electrons spin around the nucleus of an atom, which has a positive charge, and is located in the very center of the atom. The concept of "electricity" has to do with these electrons and with their "electron flow." Do you remember the example of our battery? This battery takes these negatively charged electrons from a chemical reaction inside the battery, pushes them out of the negative end of the battery, and into the wire. These electrons will then bump electrons in the atoms of the wire over and over until finally electrons arrive back at the positive end of the battery. Elements which allow this process of "bumping" those electrons on over determines how conductive the element is. So, when there's a current, it's just electrons bumping each other from atom to atom and flowing on. The individual electrons generally move very slowly, but the electric current moves at the speed of light. A circuit requires a loop for the electrons to travel on. This means you can not simply attach a wire to one end of a battery and expect electrons to flow through it. As stated before, in our definition of the circuit, a continuous loop is required. But think about it scientifically: If you did attach the wire to only one end of the battery, where would the electrons go that got bumped to the opposite end of the wire? That is why there needs to be that continuous loop of wire: the electrons need somewhere to go. AC current changes directions DC current flows in one direction only
EMF or electrical force
Electromotive force literally means, ä force that motivates electrons."
current flow and direction
If the two requirements of an electric circuit are met, then charge will flow through the external circuit. It is said that there is a current - a flow of charge. Using the word current in this context is to simply use it to say that something is happening in the wires - charge is moving. Yet current is a physical quantity that can be measured and expressed numerically. As a physical quantity, current is the rate at which charge flows past a point on a circuit. As depicted in the diagram below, the current in a circuit can be determined if the quantity of charge Q passing through a cross section of a wire in a time t can be measured. The current is simply the ratio of the quantity of charge and time. Current is a rate quantity. There are several rate quantities in physics. For instance, velocity is a rate quantity - the rate at which an object changes its position. Mathematically, velocity is the position change per time ratio. Acceleration is a rate quantity - the rate at which an object changes its velocity. Mathematically, acceleration is the velocity change per time ratio. And power is a rate quantity - the rate at which work is done on an object. Mathematically, power is the work per time ratio. In every case of a rate quantity, the mathematical equation involves some quantity over time. Thus, current as a rate quantity would be expressed mathematically as Note that the equation above uses the symbol I to represent the quantity current. As is the usual case, when a quantity is introduced in The Physics Classroom, the standard metric unit used to express that quantity is introduced as well. The standard metric unit for current is the ampere. Ampere is often shortened to Amp and is abbreviated by the unit symbol A. A current of 1 ampere means that there is 1 coulomb of charge passing through a cross section of a wire every 1 second. 1 ampere = 1 coulomb / 1 second To test your understanding, determine the current for the following two situations. Note that some extraneous information is given in each situation. Click the Check Answer button to see if you are correct. A 2 mm long cross section of wire is isolated and 20 C of charge is determined to pass through it in 40 s. A 1 mm long cross section of wire is isolated and 2 C of charge is determined to pass through it in 0.5 s. I = _____ Ampere I = _____ Ampere Conventional Current Direction The particles that carry charge through wires in a circuit are mobile electrons. The electric field direction within a circuit is by definition the direction that positive test charges are pushed. Thus, these negatively charged electrons move in the direction opposite the electric field. But while electrons are the charge carriers in metal wires, the charge carriers in other circuits can be positive charges, negative charges or both. In fact, the charge carriers in semiconductors, street lamps and fluorescent lamps are simultaneously both positive and negative charges traveling in opposite directions. Ben Franklin, who conducted extensive scientific studies in both static and current electricity, envisioned positive charges as the carriers of charge. As such, an early convention for the direction of an electric current was established to be in the direction that positive charges would move. The convention has stuck and is still used today. The direction of an electric current is by convention the direction in which a positive charge would move. Thus, the current in the external circuit is directed away from the positive terminal and toward the negative terminal of the battery. Electrons would actually move through the wires in the opposite direction. Knowing that the actual charge carriers in wires are negatively charged electrons may make this convention seem a bit odd and outdated. Nonetheless, it is the convention that is used worldwide and one that a student of physics can easily become accustomed to. Current versus Drift Speed Current has to do with the number of coulombs of charge that pass a point in the circuit per unit of time. Because of its definition, it is often confused with the quantity drift speed. Drift speed refers to the average distance traveled by a charge carrier per unit of time. Like the speed of any object, the drift speed of an electron moving through a wire is the distance to time ratio. The path of a typical electron through a wire could be described as a rather chaotic, zigzag path characterized by collisions with fixed atoms. Each collision results in a change in direction of the electron. Yet because of collisions with atoms in the solid network of the metal conductor, there are two steps backwards for every three steps forward. With an electric potential established across the two ends of the circuit, the electron continues to migrate forward. Progress is always made towards the positive terminal. Yet the overall affect of the countless collisions and the high between-collision speeds is that the overall drift speed of an electron in a circuit is abnormally low. A typical drift speed might be 1 meter per hour. That is slow! One might then ask: How can there by a current on the order of 1 or 2 ampere in a circuit if the drift speed is only about 1 meter per hour? The answer is: there are many, many charge carriers moving at once throughout the whole length of the circuit. Current is the rate at which charge crosses a point on a circuit. A high current is the result of several coulombs of charge crossing over a cross section of a wire on a circuit. If the charge carriers are densely packed into the wire, then there does not have to be a high speed to have a high current. That is, the charge carriers do not have to travel a long distance in a second, there just has to be a lot of them passing through the cross section. Current does not have to do with how far charges move in a second but rather with how many charges pass through a cross section of wire on a circuit. To illustrate how densely packed the charge carriers are, we will consider a typical wire found in household lighting circuits - a 14-gauge copper wire. In a 0.01 cm-long (very thin) cross-sectional slice of this wire, there would be as many as 3.51 x 1020 copper atoms. Each copper atom has 29 electrons; it would be unlikely that even the 11 valence electrons would be in motion as charge carriers at once. If we assume that each copper atom contributes just a single electron, then there would be as much as 56 coulombs of charge within a thin 0.01-cm length of the wire. With that much mobile charge within such a small space, a small drift speed could lead to a very large current. To further illustrate this distinction between drift speed and current, consider this racing analogy. Suppose that there was a very large turtle race with millions and millions of turtles on a very wide race track. Turtles do not move very fast - they have a very low drift speed. Suppose that the race was rather short - say 1 meter in length - and that a large percentage of the turtles reached the finish line at the same time - 30 minutes after the start of the race. In such a case, the current would be very large - with millions of turtles passing a point in a short amount of time. In this analogy, speed has to do with how far the turtles move in a certain amount of time; and current has to do with how many turtles cross the finish line in a certain amount of time. The Nature of Charge Flow Once it has been established that the average drift speed of an electron is very, very slow, the question soon arises: Why does the light in a room or in a flashlight light immediately after the switched is turned on? Wouldn't there be a noticeable time delay before a charge carrier moves from the switch to the light bulb filament? The answer is NO! and the explanation of why reveals a significant amount about the nature of charge flow in a circuit. As mentioned above, charge carriers in the wires of electric circuits are electrons. These electrons are simply supplied by the atoms of copper (or whatever material the wire is made of) within the metal wire. Once the switch is turned to on, the circuit is closed and there is an electric potential difference is established across the two ends of the external circuit. The electric field signal travels at nearly the speed of light to all mobile electrons within the circuit, ordering them to begin marching. As the signal is received, the electrons begin moving along a zigzag path in their usual direction. Thus, the flipping of the switch causes an immediate response throughout every part of the circuit, setting charge carriers everywhere in motion in the same net direction. While the actual motion of charge carriers occurs with a slow speed, the signal that informs them to start moving travels at a fraction of the speed of light. The electrons that light the bulb in a flashlight do not have to first travel from the switch through 10 cm of wire to the filament. Rather, the electrons that light the bulb immediately after the switch is turned to on are the electrons that are present in the filament itself. As the switch is flipped, all mobile electrons everywhere begin marching; and it is the mobile electrons present in the filament whose motion are immediately responsible for the lighting of its bulb. As those electrons leave the filament, new electrons enter and become the ones that are responsible for lighting the bulb. The electrons are moving together much like the water in the pipes of a home move. When a faucet is turned on, it is the water in the faucet that emerges from the spigot. One does not have to wait a noticeable time for water from the entry point to your home to travel through the pipes to the spigot. The pipes are already filled with water and water everywhere within the water circuit is set in motion at the same time. The picture of charge flow being developed here is a picture in which charge carriers are like soldiers marching along together, everywhere at the same rate. Their marching begins immediately in response to the establishment of an electric potential across the two ends of the circuit. There is no place in the electrical circuit where charge carriers become consumed or used up. While the energy possessed by the charge may be used up (or a better way of putting this is to say that the electric energy is transformed to other forms of energy), the charge carriers themselves do not disintegrate, disappear or otherwise become removed from the circuit. And there is no place in the circuit where charge carriers begin to pile up or accumulate. The rate at which charge enters the external circuit on one end is the same as the rate at which charge exits the external circuit on the other end. Current - the rate of charge flow - is everywhere the same. Charge flow is like the movement of soldiers marching in step together, everywhere at the same rate.
Voltage V or sometimes E
Imagine a battery as a super-soaker, and the water that comes out of it as voltage. The harder you pump that super-soaker, the harder that stream is going to be when it comes out of the gun. Voltage is the potential for that water to go very quickly out of the gun: the more you pumped, putting more "voltage" in, the faster that water will go: but sometimes you will have a "multi-functioning" nozzle which even allows you to adjust that water speed even further. You want the water to go out in a "wider" and "bigger" stream, you might change the nozzle to a bigger opening. What you've just done is changed the amount of space that the water is allowed to go through: the water is now given a much bigger space to flow through. The "voltage," or potential, of the water to go fast and give bruises is still high, but now you've taken away from its hitting-power by spreading it out. Anyone know where I'm going next with this? The bigger your nozzle gets (think of it like the resistance), the smaller the hitting power is going to be. Voltage is technically electrical potential. While in many cases we treat it as an absolute, it is important to remember that in circuits we talk mostly about the difference in voltage, a potential difference, and that things like Ohm's laws only apply to potential differences not just electrical potential. However, in the context of circuits, Voltage is often used in reference to potential difference.
series vs. parallel wiring components
In a series circuit, the current through each of the components is the same, and the voltage across the circuit is the sum of the voltages across each component.[1] In a parallel circuit, the voltage across each of the components is the same, and the total current is the sum of the currents through each component
use of magnets in motors
In any electric motor, rotation is caused by two magnetic fields that oppose each other. In some motors, both fields are created by coils of wire - electromagnets. In other motors, one field is electromagnetic and the other comes from one or more permanent magnets. In the permanent magnet (PM) motor, the magnetic field from the permanent magnet(s) are constant (obviously) and the other field is turned on and off, or 'commutated' at just the right time so the fields oppose, causing rotation. Commutators can be mechanical - you have probably seen the brass segments around the rotor's end that the brushes touch - this is the commutator. In some motors, mostly small cooling fans and the like, commutation can be electronic using position sensors and switching transistors. These motors are called 'brushless'. Since the power of the motor comes from the opposing magnetic fields pushing on each other, the PM motor is only as powerful as the magnets used in its construction. There is quite a bit of research going on to create very powerful magnets for high performance PM motors used in radio controlled cars, planes and other applications where a powerful yet small motor is needed.
switches
In electrical engineering, a switch is an electrical component that can break an electrical circuit, interrupting the current or diverting it from one conductor to another.[1][2] The most familiar form of switch is a manually operated electromechanical device with one or more sets of electrical contacts, which are connected to external circuits. Each set of contacts can be in one of two states: either "closed" meaning the contacts are touching and electricity can flow between them, or "open", meaning the contacts are separated and the switch is nonconducting. The mechanism actuating the transition between these two states (open or closed) can be either a "toggle
magnetic vs. non magnetic materials
Magnetic: These materials have their moments coordinated such that they point in the same direction. They therefore produce strong magnetic fields. Non-magnetic: Such substances have little reaction to magnetic fields. They may be composed of molecules where electrons spinning one way are always balanced by electrons spinning the other, or their spins may simply interact only weakly.
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Ohm's Law In DC circuits, the relationship between the current, voltage, power and resistance may be resolved with the aid of a pie chart :- There are four quadrants representing Voltage, V, Power, W, Resistance, R and Current, I. Knowing any two quantities allows the other two to be found. For example, if you have a 1k resistor and apply a voltage of 10 Volts DC across its terminals, then the current flowing through the resistor will be: V/R = 10 / 1000 = 0.01A The power dissipated in the same 1k resistor would be: V2/R = 102 / 1000 = 0.1 Watt. Depending on the flow of current, a voltage will have a polarity. The direction of current is indicated with an arrow, as shown below :- idc The side of the resistor where the current flows into the resistor will be the positive side of the voltage, the negative side is where the current flows out. If the resistor was 5 ohms and the current ( I, not one) was 2 amps, then the voltage or potential difference would be 10 volts. In electronics, it is normal to talk about potential differences (p.d.) with reference to one point, which is usually zero. If the point was not zero, then its value would be clearly indicated, but for convenience, most systems have a common ground or earth which is usually zero volts. Scientific Notation and Unit Shortcuts In electronics, often units can be very large e.g. 1M = 1,000,000 ohms or very small e.g 1uF = 0.000001F To make things easier, scientific notation is often used where the exponent is raised to the power 10. The following table contains common units and exponents . Unit Symbol Exponent Mega M x106 kilo k x103 milli m x10-3 micro u x10-6 nano n x10-9 pico p x10-12 So for example if you apply 10V DC across a 2k resistor then the current flowing is 10 / 2 x103=5 x 10-3 As the exponent x10-3 is the unit "milli" then the current is 5mA. Similarly if a resistor value is in Megaohms, then the current will be in units microamps. Series and Parallel Circuits The current in a series circuit is the same at all points. Below, 2mA is measured at any break between two points: The voltage in a parallel circuit will be the same when measured across any two points: Kirchhoff's Laws Kirchhoff's voltage and current laws are also a basic prerequisite for circuit analysis. Kirchhoff's current law simply states that the sum of currents flowing into a junction equals the sum of currents flowing away from the junction. For example:- The arrows represent the direction of current flow, the junction is where the wires meet. I1 is flowing into the junction whereas I2 and I3 are flowing out. If I1 was 20 amp and I3 was 5amp then I2 would be 15amp, as I1=I2+I3.Kirchhoff's voltage law states that the sum of voltage drops around a closed circuit is equal to zero. This can also be expressed as the sum of voltage drops around a closed circuit is equal to the sum of voltage sources :- If the diagram above, the voltage drops across R1, R2 and R3 must equal 10v or 10=V1+V2+V3. Here is an example :- The currents i2 and i3 and the unknown resistance, R can all be calculated, using basic dc theory. The direction of current flow is as indicated by the arrows. The voltage on the left hand 10 ohm resistor is flowing out of the top terminal of the resistor. The p.d. across this resistor is (i1* R ) or 5 volts. This is in opposition to the 15 volt battery. By Kirchhoff's voltage law the p.d. across the centre 10 ohm resistor is thus 15-5 or 10volts. Using ohms law, the current through the 10 ohm resistor ( V/R ) is then 1 amp. Using Kirchhoff's current law and now knowing i1 and i3, i2 is found , i3=i1+i2 therefore i2=0.5 amp. Again using Kirchhoff's voltage law the p.d. across R can be calculated. 20=i2R+10. The voltage across R ( i2R) is then 10 volts. The value of R is (V/I) or 10/0.5 or 20 ohms. A few more examples are presented under the Circuit Analysis section. Current Division The current flow at a junction will divide into two parts, the current through the respective branch can be worked out as shown below: The current through R1 can be found using the equation: I1 = IT R2 R1 + R2 The current through R2 can be found using the equation: I2 = IT R1 R1 + R2 Voltage Division The voltage across R1 can be found using the equation: VR1 = V R1 R1 + R2 The voltage across R2 can be found using the equation: VR2 = V R2 R1 + R2
ohms law
Ohm's Law (V=IR) deals with the relationship between voltage and current in an ideal conductor. This relationship states that the potential difference (voltage) across an ideal conductor is proportional to the current through it.
magnet shapes and types
Permanent Magnets These are the most common type of magnets that we know and interact with in our daily lives. E.g.; The magnets on our refrigerators. These magnets are permanent in the sense that once they have been magnetized they retain a certain degree of magnetism. Permanent magnets are generally made of ferromagnetic material. Such material consists of atoms and molecules that each have a magnetic field and are positioned to reinforce each other. Classification Permanent Magnets can further be classified into four types based on their composition: 1. Neodymium Iron Boron (NdFeB or NIB) 2. Samarium Cobalt (SmCo) 3. Alnico 4. Ceramic or Ferrite NIB and SmCo are the strongest types of magnets and are very difficult to demagnetize. They are also known as rare earth magnets since their compounds come from the rare earth or Lathanoid series of elements in the periodic table. The 1970s and 80s saw the development of these magnets. Alnico is a compound made of ALuminium, NIckel and CObalt. Alnico magnets are commonly used magnets and first became popular around the 1940s. Alnico magnets are not as strong as NIB and SmCo and can be easily demagnetized. This magnet is however, least affected by temperature. This is also the reason why bar magnets and horseshoes have to be taken care of to prevent them from loosing their magnetic properties. The last type of permanent magnets, Ceramic or Ferrite magnets are the most popular today. They were first developed in the 1960s. These are fairly strong magnets but their magnetic strength varies greatly with variations in temperature. Permanent Magnets can also be classified into Injection Moulded and Flexible magnets. Injection molded magnets are a composite of various types of resin and magnetic powders, allowing parts of complex shapes to be manufactured by injection molding. The physical and magnetic properties of the product depend on the raw materials, but are generally lower in magnetic strength and resemble plastics in their physical properties. Flexible magnets are similar to injection molded magnets, using a flexible resin or binder such as vinyl, and produced in flat strips or sheets. These magnets are lower in magnetic strength but can be very flexible, depending on the binder used. Shape & Configuration Permanent magnets can be made into any shape imaginable. They can be made into round bars, rectangles, horseshoes, donuts, rings, disks and other custom shapes. While the shape of the magnet is important aesthetically and sometimes for experimentation, how the magnet is magnetized is equally important. For example: A ring magnet can be magnetized S on the inside and N on the outside, or N on one edge and S on the other, or N on the top side and S on the bottom. Depending on the end usage, the shape and configuration vary. Demagnetization Permanent magnets can be demagnetized in the following ways: - Heat - Heating a magnet until it is red hot makes it loose its magnetic properties. - Contact with another magnet - Stroking one magnet with another in a random fashion, will demagnetize the magnet being stroked. - Hammering or jarring will loosen the magnet's atoms from their magnetic attraction. Temporary Magnets Temporary magnets are those that simply act like permanent magnets when they are within a strong magnetic field. Unlike permanent magnets however, they loose their magnetism when the field disappears. Paperclips, iron nails and other similar items are examples of temporary magnets. Temporary magnets are used in telephones and electric motors amongst other things. Electromagnets Had it not been for electromagnets we would have been deprived of many luxuries and necessities in life including computers, television and telephones. Electromagnets are extremely strong magnets. They are produced by placing a metal core (usually an iron alloy) inside a coil of wire carrying an electric current. The electricity in the current produces a magnetic field. The strength of the magnet is directly proportional to the strength of the current and the number of coils of wire. Its polarity depends on the direction of flow of current. While the current flows, the core behaves like a magnet. However, as soon as the current stops, the core is demagnetized.
Resistors
Resistor Color Codes Color Value Black 0 Brown 1 Red 2 Orange 3 Yellow 4 Green 5 Blue 6 Purple(Indigo) 7 Gray 8 White 9 Gold .1 Silver .01 Common Tolerance Codes Color Percent Silver 10% Gold 5% Red 2% Brown 1% the most common tolerance you will see is Gold, followed by Brown To convert the color codes into resistance values(on a resistor with 3 bands and a tolerance band) read the first two bands off in order and then multiply that by 10^(color of third band), so the picture would be 56x10^0 which is 56 ohms. If the resistor has more than 4 bands, all you do is read the first howevermany(normally 3) until you only have one color(not tolerance) left, and multiply by 10^last color band
the unit of measurement for ressistance
The SI unit of electrical resistance is the ohm (Ω), while electrical conductance is measured in siemens (S).
magnetic south pole
The South Magnetic Pole is the wandering point on the Earth's Southern Hemisphere where the geomagnetic field lines are directed vertically upwards. It should not be confused with the lesser known South Geomagnetic Pole described later. For historical reasons, the "end" of a magnet that points (roughly) north is itself called the "north pole" of the magnet, and the other end, pointing south, is called magnet's "south pole". Because opposite poles attract, the Earth's South Magnetic Pole is physically actually a magnetic north pole (see also North Magnetic Pole - Polarity). The Earth's geomagnetic field can be approximated by a tilted dipole (like a bar magnet) placed at the center of the Earth. The South Geomagnetic Pole is the point where the axis of this best-fitting tilted dipole intersects the Earth's surface in the southern hemisphere.
electromagnetic principals
The transformer is based on two principles: first, that an electric current can produce a magnetic field and second that a changing magnetic field within a coil of wire induces a voltage across the ends of the coil
ohms law
This article is about the law related to electricity. For other uses, see Ohm's acoustic law. V, I, and R, the parameters of Ohm's law. Ohm's law states that the current through a conductor between two points is directly proportional to the potential difference across the two points. Introducing the constant of proportionality, the resistance,[1] one arrives at the usual mathematical equation that describes this relationship:[2] where I is the current through the conductor in units of amperes, V is the potential difference measured across the conductor in units of volts, and R is the resistance of the conductor in units of ohms. More specifically, Ohm's law states that the R in this relation is constant, independent of the current.[3] The law was named after the German physicist Georg Ohm, who, in a treatise published in 1827, described measurements of applied voltage and current through simple electrical circuits containing various lengths of wire. He presented a slightly more complex equation than the one above to explain his experimental results. The above equation is the modern form of Ohm's law. In physics, the term Ohm's law is also used to refer to various generalizations of the law originally formulated by Ohm. I=V/R or current equals volts over resistance resistance is constant power equals voltage times current or V x I power is in watts
Application of Ohms Law
This section doesn't teach any theory behind Ohm's law, but this is one of the easiest ways to apply the law(or the power law(P=IV), or any similar law). Basically, take a circle and divide into half, then divide one of the halfs in half again(so you have half a circle at the top, and two quarters at the bottom). Then you put the equation(any equation in the form a=bc), in the case of the power law, P would go into the half, and I and V would go into quarters. Now all you have to do to find a certain value is cover up what you're looking for(for example,finding I using P and V) and look at the 2 uncovered letters, in the example, P and V are uncovered, since P is on top of V, we know that I=P/V, if the letters are next to each other(i.e. finding P from I and V) then you simply multiply. Sure, the math behind it is very simple, but in a competition this method goes a lot quicker than rearranging equations.
Physical points of Voltage, Current, and Resistance
Voltage is always measured between two points. Current may be measured at a single point (at a cross-section of a conductive path). Resistance is always measured between two points. Follow-up question: explain, if you can, the relevance of these facts to electrical safety. For example, why is it important to know that voltage is always a quantity existing between two points (rather than existing at a single point) when considering your personal safety?
earth's magnetic fields
Web definitions Earth's magnetic field is the magnetic field that extends from the Earth's interior to where it meets the solar wind, a stream of charged particles emanating from the Sun. Its magnitude at the Earth's surface ranges from 25 to 65 µT. .
wet vs. dry cells
Wet cell batteries, sometimes called flooded, are made from a glass or plastic container filled with sulfuric acid in which lead plates are submerged. They were the first rechargeable batteries, invented in 1859, but are still in common use today in automobiles, trucks, RVs, motorized wheelchairs, golf carts and emergency power backup systems in household and industrial applications. The main concern for wet cell batteries in all applications is leaking sulfuric acid, as it is a dangerous corrosive that can damage what it contacts and can burn human tissue. Although there are many types of dry cell batteries that do not contain liquid that can be spilled, the main competitors with wet cell batteries are gel cells and absorbent glass mat (AGM) batteries. The main difference is that the sulfuric acid is not in liquid from, and therefore leaking is much less of a hazard. The smaller types of dry cell batteries, such as alkaline or nickel-cadmium, usually cannot be manufactured in sizes or prices that could compete with the wet cells. So the decision is really between a wet cell, a gel cell or absorbent glass mat.
capacitors
a device for accumulating and holding a charge of electricity, consisting of two equally charged conducting surfaces having opposite signs and separated by a dielectric.
operation of an electromagnet
an electromagnet is operated by wrapping a iron nail or other piece of iron in copper wire, and attaching the wire to an electrical energy source
magnetic north pole
he North Magnetic Pole is the point on the surface of Earth's Northern Hemisphere at which the planet's magnetic field points vertically downwards (in other words, if a magnetic compass needle is allowed to rotate about a horizontal axis, it will point straight down). There is only one location where this occurs, near (but distinct from) the Geographic North Pole and the Geomagnetic North Pole. The North Magnetic Pole moves over time due to magnetic changes in the Earth's core Earth's north magnetic pole is racing toward Russia at almost 40 miles (64 kilometers) a year due to magnetic changes in the planet's core, new research says.
ohms
he ohm (symbol: Ω) is the SI derived unit of electrical resistance, named after German physicist Georg Simon Ohm. Although several empirically derived standard units for expressing electrical resistance were developed in connection with early telegraphy practice, the British Association for the Advancement of Science proposed a unit derived from existing units of mass, length and time and of a convenient size for practical work as early as 1861. The definition of the "ohm" unit was revised several times. Today the value of the ohm is expressed in terms of the quantum Hall effect.The ohm is defined as a resistance between two points of a conductor when a constant potential difference of 1.0 volt, applied to these points, produces in the conductor a current of 1.0 ampere, the conductor not being the seat of any electromotive force.[1]
Energy
is the capacity for doing work. You must have energy to accomplish work - it is like the "currency" for performing work. To do 100 joules of work, you must expend 100 joules of energy.
Power
is the rate of doing work or the rate of using energy, which are numerically the same. If you do 100 joules of work in one second (using 100 joules of energy), the power is 100 watts.
the unit of measurement for current
one coulomb per second
Work
refers to an activity involving a force and movement in the directon of the force. A force of 20 newtons pushing an object 5 meters in the direction of the force does 100 joules of work.
power source
the power source of a circuit is the battery
voltmeter measurments
voltmeters measure the voltage gain at the battery or source drop or loss at the light bulb. symbol for voltage is a capitol V. in a circuit voltage gains equal voltage losses.
the unit of measurement for voltage
volts, or Joules per coulomb
kitchen built batteries
you build a kitchen built battery by using a lemon or potato,bare copper wire, and a galvanized nail. If you use a voltmeter and probe the two pieces of metal you will see a voltage. If you hook enough of these up in series you can light up a small LED bulb.
