...P7/P8 Magnetic Field Characteristics report. Magnetic Flux and Flux Density- The magnetic flux of a material is the amount of magnetic field or magnetic flux density passing through a surface. You can calculate this by finding the average magnetic field times the perpendicular area. Magnetic flux is given the symbol Φ and is measured in units called Webers (Wb). For a closed surface, the sum of magnetic flux is always equal to zero. The magnetic flux density can also be known as the density of magnetic lines of force that pass through specific area. The flux density is measured in the units of ‘tesla’. 1 T is equal to 1 Wbm -2 . After analysing the B/H graph below you can see that the more magnetic field strength the greater flux density, if we look at the steel, when it reaches a flux density value of 1.5 then it reaches its magnetic saturation this is when it can’t increase the magnetization of the material further, this means that the flux density will more then likely level off. The flux density increases highly as the field strength increases than when it reaches the magnetic saturation point then it won't increase much more. The magnetic saturation point puts a limit on the maximum effective strength to drive your coil. There will be no benefit at all if you exceed this, only wasted heat. Excess heat on the coil can also cause it to fail. The material permeability maximum point is when the graph starts to curve and go away from the straight positive correlation line...
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...Electric Current and Magnetic Field. Md Hisham (13) Md Farith (14) Casper Teng (2) Md Ruzaini (20) Daniel Deskar (6) Tijany Sulaiman (28) 1. What is electric current? A movement or flow of electrically charged particles, typically measured in amperes. An electric current is a flow of electric charge. In electric circuits this charge is often carried by moving electrons in a wire. It can also be carried by ions in an electrolyte, or by both ions and electrons such as in a plasma. Electric current can consist of a flow of charged particles in either direction. The conventional symbol for current is I 1. Working principles of Electric Current....
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...they have a relatively same slope, it shows that ohms law is valid. Experiment 3 The reason why putting brass in the coil did not induce a current is that brass is not magnetic. Therefore it does not create a magnetic field inside the coil and therfore no change in flux is generated. The iron produces a larger induced current and since iron is magnetic, it does generate a magnetic field inside the coil and therefore changes the magnetic flux inside the coil and the coil then generates a current to oppose that flux. According to Faraday's law you need a change in the magnetic flux to induce a magnetic field. Because the wire is not moving, there is no induced magnetic field. Initially the small coil inside the large coil genrates a change in magnetic flux through its inherent current. The large coil then generates a current to oppose that flux, which represents the initial spike in the graph. The decrease in voltage is due the large current opposing the flux and thereby reducing its voltage. Once the voltage reaches zero, there is no flux to oppose the change generated by the small coil, which is why the voltage spikes again, this time in the other direction due to the nature of the square wave voltage. Experiment 6 The electric field is reduced by a factor of cos theta after the light passes through the polarizer. The intensity of...
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...Magnetic flux: The force of a magnet from the north pole to the south pole. Magnetic flux density: The amount of flux per unit area perpendicular to the magnetic field. Weber: SI unit of magnetic flux. (Wb) Tesla: SI unit of flux density, equal to one weber per square meter. Gauss: unit from the CGS (centimeter-gram-second) system, unit of flux density. Hall Effect: The change in current density produces a small trans- verse voltage in the material. Electromagnet: Produces a magnetic field only when there is current through a conductor. Reluctance: the opposition to the establishment of a magnetic field in a material. Permeability: the ease with which a magnetic field can be established in a given material is measured by Permeability of that material. Solenoid: A type of electromagnetic device that in which the mechanical movement of a shaft or plunger is activated by a magnetizing current. Relay: An electromagnetically controlled mechanical device in which electrical contacts are opened or closed by a magnetizing current. Faradays law: A law stating that the voltage induced across a coil equals the number of turns in the coil times the rate of change of the magnetic flux. Shunt dc motor: Type of motor that has a torque-speed characteristic. Period of a wave: Time required for a given sine wave to complete one full cycle. Frequency of a wave: number of cycles that a sine wave completes in...
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...Diagram 1 Diagram 1 Magnetic fields are everywhere any item that uses a magnet generates one. The magnetic field of a magnate can be likened to the lines of magnetic flux which are basically the amount of magnetic field an item has. You can demonstrate the lines of flux through the iron filings experiment where you place a magnate in a dish of iron fillings and it will show the line of flux (see diagram 1 ) The lines of flux flow from the South Pole to the North Pole within a material where as in the air they will flow from North Pole to South Pole. The lines will always seek the path of least resistant’s between poles; this is why they will first form the close loops to the object. The lines get further and further out because the lines of force are all the same value and will never cross each other so this means the distance between the magnet and the loops increases the density decreases there for the magnetic field strength decreases the further away from the magnet it gets. The size of a magnet does not affect the magnetic field strength of a magnet but will affect the flux density because a larger magnet would have a larger dimensional area and volume, so the loops would be more spread out when flowing from pole to pole. A smaller magnet, however, would have a smaller area and volume so the loops would be more concentrated. Diagram 2 Diagram 2 When you put two magnets together they will either repel or attract (see diagram 2) if north to north they will repel ...
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...Intrpduction : Maglev systems are becoming a popular application around the globe. Maglev trains are popular in transportation stations in big countries like Germany, China, Japan and the United States of America due to the demand for high-speed transportation, as the general public transportation services become more congested with increase of population. Maglev trains are magnetically levitated trains that traverse in a very high speed, with only electricity being its main source of energy. The train propels forward without any friction from moving mechanical parts. It has many advantages with minor drawbacks. The basis of maglev trains mechanisms are magnetic levitation. This is achieved with the principal of repulsion and attraction between two magnetic poles. When two magnets have the same poles, it will repel with each other and when it has different poles, the result would be otherwise. There are currently three known maglev suspension systems. In this project report, we will be covering the basic principals of Electrodynamic Suspension Systems (EDS), Electromagnetic Suspension Systems (EMS) and Inductrack. The three suspension systems each have different characteristics and special features. While EDS and EMS both use only the interaction of magnets and superconductors, Inductrack uses coils on the track underneath the train body. All three suspension systems work under the same principal of magnetic levitation covered in this project report. The maglev propulsion...
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...Induction – Magnet through a Coil Activity P30 Purpose: Electromotive forces can be induced in a coil by changing the magnitude of the magnetic field within the coil, changing the area of the coil, or changing the angle between the magnetic field and the area of the coil. This lab used the first method of changing the magnitude of the magnetic field by dropping a magnet through a coil in order to induce an electromotive force. The EMF was measured as the magnet fell. The integral of EMF versus time gives the magnetic flux according to Faraday’s Law of induction. Faraday’s law of induction essential states that EMF is equal to the rate of change of magnetic flux. Some aspects of Lenz’s law were also investigated. Lenz’s law states that the direction of the current in a coil moves in the direction that causes a magnetic field that opposes the change in the magnetic field of the magnet. Procedure and Materials: The computer was set up by connecting the Voltage Sensor and the interface. A new activity was opened in Data Studio with a graph of Voltage versus Time. Automatic recording was set to begin recording once 0.05 volts was reached and stop at 0.4 seconds of elapsed time. The alligator clips were connected to the circuit board springs next to the induction coil. Data was recorded for three variations of the experiment. First, a single bar magnet was dropped through the coil starting with the south end approximately 2 cm above the coil. Then two magnets were dropped with...
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...Jonathan Frost 1-8-14 Single Phase AC Motors Single phase AC motors are a type of motor that is what the name implies which is one phase. In a single phase AC motors, a single phase motor has voltage and it splits into two phase currents to create a rotating magnetic field to generate the rotor. There are four different types of single phase AC motors and they are called split phase, capacitor, shaded pole, and repulsion. Capacitor and shaded pole is the most common motors they have. A capacitor run motor is connected between a main and auxiliary winding to create a phase shift in between the windings and a rotating flux. Split phase has main and auxiliary winding a centrifugal switch open and remove the auxiliary winding. It reverses at low speed, relatively cheap cost, and it has rapid acceleration. A single coil of a single phase motor doesn’t produce a rotating magnetic field, but a pulsating field could reach maximum intensity at 0 degrees and 180 degrees electrical. A single phase current and can produce two counter rotating magnetic field phases. Permanent-split capacitor motor have one way to solve a single phase problem is to build a 2- phase motor. It requires a motor with 2 windings spaces away 90 degrees electrical and displace two phases of current with 90 degrees in time. Permanent – split capacitor motor has increased current magnitude and also has a backwards time shift as the motor generates the speed pace. The motor works well...
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...Patel______________________________________________ TA Alec Sim_____________________________________________ Role | I | DC | AD | RC | Q1 | Q2 | PI | PG | | | | | | | | | | | | | | | | | | | | | | | | | | | | I introduction DC data and calculation AD analysis and discussion RC results and conclusion Q1/Q2 quiz/prelab PI principal investigator points PG personal grade Introduction: The purpose of the lab is to study the effects due to magnetic fields in motion and also to determine the qualitative features of electromagnetic induction. Procedure: 1. For the Part 1 of the lab, a solenoid was connected to a galvanometer, as shown in the data and calculations. First, the North pole was inserted into the coil, then in the opposite direction, with the South Pole first. Then, the magnitude and sign of the deflection on the galvanometer was recorded in μAmps. Also, an exact sketch is made of the solenoid, the direction of the velocity, the induced magnetic field, the induced current and the magnetic polarity of the solenoid induced in provided in the data and calculations portion of the report. 2. The magnet was inserted again following step 1, but with a faster speed and everything sketched again. Then, The South pole was inserted first and step 1 followed again for both, slow and fast speed. 3. For Part II of the lab, an electromagnet was constructed with the power supply off. In this set up the primary coil had a larger diameter...
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...effect of armature reaction in a DC machine. i) By increasing the length of air gap at pole tips ii) By increasing the reluctance at pole tips iii) Providing compensating winding and interpoles. 2. List the advantages of lap winding in a DC machine. i) Reduction of weight of armature core ii) Cost of armature and field conductors iii) Overall length and diameter of machine. 3. State the relationship between number of armature coils and number of commutator segments in a dc machine. The relationship between number of armature coils and number of commutator segments in a dc machine is where - commutator segment pitch C- no. of coils D- diameter of commutator 4. State different losses in a dc generator. a) Copper losses: (i) armature copper loss (Ia2 Ra) ii) field copper loss (I2snRsh, I2seRse) b) Magnetic losses ( iron or core loss): i) hysteresis loss (Whα B1.6maxf) ii) eddy current loss(Weα B2maxf) iii) mechanical losses 5. What are the main dimensions of a rotating machine? The main dimensions of a rotating machine are armature diameter and stator core length. 6. Define specific magnetic loading. It is defined as the average flux density over the air gap of the machine. Specific magnetic loading = 7. Define specific electric loading. It is defined as the no of armature conductors per meter of armature periphery at the air gap. Specific electric loading = 8. What is output equation? The equation describing the relation between the output and...
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...magnetic field 4) Equivalent circuit model 5) Performance as a generator 6) Performance as a motor Introduction A synchronous machine is an ac rotating machine whose speed under steady state condition is proportional to the frequency of the current in its armature. The magnetic field created by the armature currents rotates at the same speed as that created by the field current on the rotor, which is rotating at the synchronous speed, and a steady torque results. Synchronous machines are commonly used as generators especially for large power systems, such as turbine generators and hydroelectric generators in the grid power supply. Because the rotor speed is proportional to the frequency of excitation, synchronous motors can be used in situations where constant speed drive is required. Since the reactive power generated by a synchronous machine can be adjusted by controlling the magnitude of the rotor field current, unloaded synchronous machines are also often installed in power systems solely for power factor correction or for control of reactive kVA flow. Such machines, known as synchronous condensers, may be more economical in the large sizes than static capacitors. With power electronic variable voltage variable frequency (VVVF) power supplies, synchronous motors, especially those with permanent magnet rotors, are widely used for variable speed drives. If the stator excitation of a permanent magnet motor is controlled by its rotor position such that the stator field is always...
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...Episode 412: The force on a conductor in a magnetic field Having reminded your students that magnetic fields can be found near permanent magnets and in the presence of an electric current, the next step is to show how the ‘field’ can be quantified. Again, students should know that a conductor carrying a current in a magnetic field will experience a force and will probably remember that Fleming's Left Hand Rule can be used to find the direction of that force. Summary Demonstrations: Leading to F = BIL. (15 minutes) Discussion: Factors affecting the force. (15 minutes) Discussion: Formal definitions. (20 minutes) Student questions: BIL force calculations. (20 minutes) Demonstrations: Leading to F = BIL Several quick experimental reminders are possible. Tap 412-1: Forces on currents TAP 412-2: An electromagnetic force These lead on to a further experiment in which the relationship F=BIL can be established. TAP 412-3: Force on a current-carrying wire Discussion: Factors affecting the force The experiments above lead to the conclusion that the force F on the conductor is proportional to the length of wire in the field, L, the current I and the ‘strength’ of the field, represented by the flux density B. (There is also an 'angle factor' to consider, but we will leave this aside for now.) Combining these we get F = BIL (It can help students to refer to this force as the ‘BIL force’.) Students...
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...permanent magnet is one that retains its magnetic properties for a long period of time. A temporary magnet only maintains its magnetism while in the magnetic field produced by a permanent magnet or an electric current. Example of permanent magnets: the magnets on our refrigerator used to hold notes on a refrigerator door. These magnets are permanent in the sense that once they have been magnetized they retain a certain degree of magnetism Example of temporary magnets: Paperclips, iron nails and other similar items are examples of temporary magnets. Temporary magnets are used in telephones and electric motors amongst other things List examples of magnetic materials and nonmagnetic materials Magnetic materials: iron, cobalt, nickel, steel, some alloys of rare earth materials Nonmagnetic materials: rubber, plastic, stainless steel, paper, silver, List the basic features of a magnet 1. Magnets attract objects of iron, cobalt and nickel. 2. The force of attraction of a magnet is greater at its poles than in the middle. 3. Like poles of two magnets repel each other. 4. Opposite poles of two magnets attracts each other. 5. If a bar magnet is suspended by a thread and if it is free to rotate, its South Pole will move towards the North Pole of the earth and vice versa. List the characteristics of magnetic flux 1. Magnetic lines of force start from...
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...Massachusetts Institute of Technology Department of Electrical Engineering and Computer Science 6.685 Electric Machines Class Notes 1: Electromagnetic Forces c 2003 James L. Kirtley Jr. September 5, 2005 1 Introduction Bearings Stator Stator Conductors Rotor Air Gap Rotor Conductors Shaft End Windings Figure 1: Form of Electric Machine This section of notes discusses some of the fundamental processes involved in electric machinery. In the section on energy conversion processes we examine the two major ways of estimating electromagnetic forces: those involving thermodynamic arguments (conservation of energy) and field methods (Maxwell’s Stress Tensor). But first it is appropriate to introduce the topic by describing a notional rotating electric machine. Electric machinery comes in many different types and a strikingly broad range of sizes, from those little machines that cause cell ’phones and pagers to vibrate (yes, those are rotating electric machines) to turbine generators with ratings upwards of a Gigawatt. Most of the machines with which we are familiar are rotating, but linear electric motors are widely used, from shuttle drives in weaving machines to equipment handling and amusement park rides. Currently under development are large linear induction machines to be used to launch aircraft. It is our purpose in this subject to develop an analytical basis for understanding how all of these different machines work. We start, however, with a picture of perhaps...
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...Faraday’s Law In 1820 Hans Christian Oersted observed that electric currents create magnetic fields. Consequently many scientists made unsuccessful attempts to create current in the presence of magnetic fields. After over 10 years of investigation Michael Faraday and Joseph Henry, working independently on different sides of the Atlantic, made the discovery that if a conducting coil has a changing magnetic flux passing through it an electromotive force is created that causes a current to flow through the coil. The equation describing this phenomenon quantitatively is known as Faraday’s Law. a b c In this activity you will be asked to use Faraday’s Law to explain why the current induced in a coil and thus the voltage across it changes the way it does when the north or south pole of rod shaped magnet is moved into and then back out of the center of a coil of wire at various speeds. No calculations are required in this activity, just thinking! Figure 1: The north pole of a cylindrical magnet is: (a) moving into the center of a coil of wire; (b) reversing direction; and then (c) moving out of the coil. The coil’s voltage vs. time is recorded with a computer interfaced voltage probe. Theoretical Review: According to Faraday’s Law, at any moment the induced emf (denoted ) across a conducting loop with N turns is equal to –N times the rate of change of the magnetic flux passing through the area enclosed by the loop as described in Eq. 1. (Faraday’s Law) [Eq. 1]...
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