Electromagnetic induction - Assignment Example

In electromagnetic induction, a current carrying wire induced a magnetic field around the wire. Cutting the field using a magnet will result to an induced emf, which is proportional to the rate of change of the magnetic field or speed at which the field is cut. This is the Faraday’s law being investigated in this experiment. on the other hand, the experiment portrays that the magnetic flux will always act as to oppose any change in a closed loop, which is the Lenz’s law investigated in this experiment. The results showed that the polarity of the induced voltage opposed the charge producing it, with the speed of the magnet cutting the field being propotional to the emf induced. Moreover, when testing the polarity of a transfomer using a small DC voltage, amplification of the volatge indicated a positve polarity and reduction a negative one. The experiment was thus succesful in testing the two laws above. Practical: Electromagnetic Induction In magentic induction, the induced elctromotive force or emf in a closed circuit would be equivalent to the time rate of the magetive flux passing through the circuit. Electromitive force, emf is the engery gained per unit charge that passes through an elctric conductor such as a generator. Emf in any circuit is measured in Volts, and a source to give the emf is applied to power up the cicuit (Breithaupt, 2000). On the other hand, in magentic induction, magenitic fluix will refer to the amount of magnetism, or the strength of a specific magnetic field. Two laws are important in understanding and explaining electromagentic induction. These are the Faraday’s l;aw and Lenz’s law. Farad’s law states that any charge passing through a magnetic field of a coil of wire will produce avoltage (emf) to be induced in the conductor. A voaltge will always be produced despite the charge of the conductor or the magenitc field. The figure below summarizes Farady’a Law by explaining how voltage is generated between a conductor and a magnetic field in what is termed as magnetic induction. On the other hand, Lenz’s law is an important law that explains how magnetic induction occurs, and how flux is generated in a magnetic field. In the definition of Faraday’s law above, any emf generated by a charge in a magnetic flux will have a polarity of the induced emf in a way that produces current, with a magnetic field opposing the charge producing it. Therefore, Lenz law explains that the induced magnetic field in a loop of wire will at any time act to keep the magnetic flux in the loop constant. That is; an induced field will always act in the direction of an applied field in trying to keep it constant. This experiment was aimed at demonstrating the two laws and their applicability magnetic induction. Aim The aim of the practical was to investigate the behaviors of coils and magnets in a magnetic field created by current, testing Faraday’s and Lenz’s laws, and testing the behavior of a transformer that uses the two laws above to produce electric current. Equipment provided Coils, LV transformer DC voltage source Analogue multimeter/ galvanometer Bar magnets and small compass. Safety Precautions in the Experiment Safety shoes were worn throughout the experiment, no damaged equipment or tool was used in the experiment, and all electric connections were ensured to have a grounding connection. In addition, before the experiment, all electrical equipment was well grounded to avoid any shaking, which could affect data collection. Procedure Two magnetic bars were placed and a compass used to trace any presence of a magnetic field and its direction at different points around the two magnetic bars as shown below. In measuring Iin In measuring inductance, an electronic bridge was used to measure the inductance of an air-core coil. The coil resistance was recorded, and the relevant dimensions of the set up measured and recorded. The following formula was then used to detect the number of turns of the coil L = N2µA/l where N= number of turns µ= 4π x 10-7 A= cross sectional area and l= is he length of coil Investigating magnetic induction Using the magnetic coil, the galvanometer and the oscilloscope, Lenz and Faraday’s laws were investigated by moving the magnet relative to the coil, and then connecting the oscilloscope and galvanometer to observe the emf induced when moving the magnet and the arrangement that resulted to the greatest output sketched as below. Magnetic Flux The 45V AC supply was connected to a 500 turn winding and the peak intensity of the magnetic flux in the small transformer determined using the formula: mmf = N.I φ=mmf/R where R= l/µ0µrA and µ0= 4π x10-7 Transformer Kick Test The polarities of a transformer winding were investigated by connecting a 10V DC source to the transformer’s highest voltage output terminals. A meter was connected to the LV secondary terminals and polarity of the reading observed as shown in the below set up; Square Wave Response The signal generator was set to produce a 1 KHz square waves and the voltage level set at about 3Vp-p. The generator was connected to the transformer’s highest voltage output terminals and the output measured on the LV terminals and the observations recorded with the waveform being sketched. Results The coil resistance was recorded was 2.150η, with Ns as 221 turns In moving the magnet in the magnetic field, a high speed was observed to result to a high output while a low speed resulted to a low voltage output. Removing the core of meant no current was produced; this is because the core had to cut the magnetic flux for any observation to be observed. In addition, changing the current through the coil resulted in an induced voltage due to the changing electromagnetic field and the polarity of the induced voltage was observed to oppose the charge producing it. In the transformer kick start, positive voltage when applied was observed to result in a positive when connected and a negative when disconnected, for the negative voltage, the vice versa applied. Moreover, in the square wave response the input was observed to result in the pattern of wave shown in (a) below without load and b with load. As observed for the two wave patterns. Discussion From this experience, it can be clearly stated that inductance is entirely caused by a magnetic field that created by current. From the first experiment of a conductor cutting the field of a current carrying wire, when the conductor magnet was constant, the magnetic field was also constant. This implied that due to the flux linking the coil, the magnetic field was not changing (Robbins & Miller, 2003). From the experiment increasing the current increased the opposing voltage in the magnetic field. On the other hand, decreasing the current was observed to reverse the polarity of induced voltage. In other words, the collapsing field resulted in a voltage that tried to keep the current constant or increasing. Therefore, the experiment was observed to obey both Faraday and Lenz law. Lenz’s as earlier described indicates that collapsing a magnetic field will always result to a current that tries to keep the current going or constant; this is the principle behind reversing the polarity as the magnet is drawn away (Newman, 2004 ). Likewise, increasing the current resulted in a voltage that opposed the buildup of more current. Therefore, Faraday’s law was also successfully investigated in that in the experiment, moving the magnet slowly resulted into a low voltage, while the voltage increased as the speed increased. Since the magnet was cutting the magnetic field created by the current, this phenomena was observed to obey Faraday’s law that the induced emf has to be proportional to the rate at which the magnet moved. In other words, the emf induced in a circuit depends on the time of change of the magnetic flux in the circuit (Fitzpatrick, 2007). On the other hand, the experiment on testing the polarity of a transformer indicated that the operation of a transformer depends on the orientation of both the primary and secondary coils (Anonymous, 2012). Testing the polarity of a transformer involves identifying which is the primary and secondary terminal when these markings are not indicated. Connecting a battery in series and negative terminal to the unmarked (left hand brushing) terminal of the transformer, and making an instantaneous contact between the marked side and positive side of the battery resulted in an upscale initial kick when the setup was connected meaning the measured voltage is greater than applied voltage and this indicates a positive polarity, and subtractive if the measured voltage is smaller than applied (Kilowatt classroom, 2002). In other words, the positive voltage resulted to a positive voltage when the connection is on, and negative when broken. Thus the polarities showed that if the windings are connected to the positive polarity, the current will tend to flow in the opposite direction, while if connected on the negative polarity, current will tend to flow in the same direction (Stallcup & Stallcup, 2012). The transformer was supposed to produce square wave in its pulse behavior with perfect square wave indicating that the transformer was in perfect condition (Digital Energy, 2012). However, because internal problems in the transformer as a result of resistance and other deformities, the waveform was somehow not uninform. Therefore, the experiment may have been affected by resistance and other deformities within the used equipment. Conclusion and Recommendation The experiment was a success as it successfully investigated both Lenz and Faraday laws of electromagnetic induction, and how induction is applied in transformers to produce current from the primary to the secondary coils. The experiments clearly indicated the relationship of magnetic field and induced emf when the field is cut by a magnet, which is the basic principle in use in a transformer. However, the experiment may have suffered from the use of faulty equipment as portrayed by the irregular wave observed in testing the polarity of the transformer. It will be recommendable to carry out more detailed experiment on: - To investigate other areas that the two laws above are applied in understanding the laws of electromagnetic induction better. - A more detailed experiment on product of electricity through the magnetic induction principles All the same, the experiment was successful and led to an informed knowledge regarding how electromagnetic induction is achieved and its applicability in a transformer. Learning Evaluation The experiment was very helpful in investigating the application of Farad and Lenz laws in electromagnetic induction. Through the experiment, the idea of a current carrying conductor creates a magnetic field, and the effects of cutting such field using a magnet was better understood and appreciated the applicability of this principle in numerous electrical applications. The experiment particular in testing the polarity of a transformer may be broadened to included production of electric current though electromagnetic induction in transformers, as it is practically done in national power stations. This will offer particle knowledge on how electricity is produced and transmitted for use using the grid. References Anonymous, 2012. Chapter 22: Electromagnetic Induction http://www.physics.ohio-state.edu/~humanic/p112_lecture13.pdf Breithaupt, J., (2000) New Understanding Physics for Advanced Level Fourth Ed. Cheltanham: Nelson Thornes Digital Energy (2012). Instrument Transformer Basic Technical Information and Application http://www.gedigitalenergy.com/products/brochures/ITItechInfo.pdf Fitzpatrick, R., 2007.Faraday’s Law http://farside.ph.utexas.edu/teaching/316/lectures/node85.html Kilowatt Classroom (2002). Transformer polarity http://www.idc-online.com/technical_references/pdfs/electrical_engineering/Transformer_Polarity.pdf Newman, J., (2008) Physics of the Life Science. NY: Springer Robbins A.H., & Miller W.A.R., (2004) Circuit analysis with Devices Theory and Practice NY: Cengage Learning. Stallcup, J.G., & Stallcup J.W. (2012). Stallcup’s Generator, Transformer, Motor and Compressor , 2011 ed. MA: Jones & Bartlett Read More