Three Phase Systems

Three Phase Systems Determine the neutral current in the unblanced 4-wire star power system shown in figure1. Express the answer in both complex number and polar forms. Use a simulator to confirm the magnitude of the nuetral current which is eqaluated. Given that, Z1 = 40 à ¢Ã‹â€ Ã‚  50 ° Z2 = 10 à ¢Ã‹â€ Ã‚  30 ° Z3 = 25 à ¢Ã‹â€ Ã‚  60 ° V1 = 230 à ¢Ã‹â€ Ã‚  0 ° V2 = 230 à ¢Ã‹â€ Ã‚  120 ° V3 = 230 à ¢Ã‹â€ Ã‚  240 ° à ¯Ã¢â‚¬Å¡Ã‚ § To Find Neutral Current by Calculation: To find the neutral current, first we have to find I1, I2 and I3 and then add them together to get the neutral current. à ¯Ã¢â‚¬Å¡Ã‚ § To find I1: I1 = I1 = I1 = I1 = (5.75 ) A (Polar Form) Current in Rectangular Form: I1 = (3.69 -j 4.40) A à ¯Ã¢â‚¬Å¡Ã‚ § To find I2: I2 = I2 = I2 = I2 = (23 90) A (Polar Form) Current in Rectangular Form: I2 = (0 +j 23) A à ¯Ã¢â‚¬Å¡Ã‚ § To find I3: I3 = I3 = I3 = I3 = (9.2 180) A (Polar Form) I3 = (-9.2 +j 0) A (Rectangular Form) Now to find neutral current IN, we need to add I1, I2 and I3 IN = I1 + I2 + I3 IN = (3.69 -j 4.40) + (0 +j 23) + (-9.2 +j 0) IN = (3.96 + 0 9.2) +j (-4.40 + 23 + 0) IN = (-5.51 +j 18.6) A (Rectangular Form) IN = 19.39 106.50 A (Polar Form) à ¯Ã¢â‚¬Å¡Ã‚ § Using TINA Simulation: Use the three-wattmeter method on a simulator to determine the total effective power dissipated in Figure1. Confirm this answer by calculation. à ¯Ã¢â‚¬Å¡Ã‚ § Using TINA Simulation: à ¯Ã¢â‚¬Å¡Ã‚ § Total Effective Power Dissipated in Figure1 by Calculation: To find total effective power dissipated, first we have to find P1 eff, P2 effand P3 eff à ¯Ã¢â‚¬Å¡Ã‚ § To find P1 eff : P1 eff P1 eff = cos 50 P1 eff = 850 W à ¯Ã¢â‚¬Å¡Ã‚ § To find P2 eff : P1 eff P2 eff = cos 30 P2 eff = 4581.27 W à ¯Ã¢â‚¬Å¡Ã‚ § To find P3 eff : P1 eff P1 eff = cos 60 P1 eff = 1058 W P total = P1 eff + P2 eff+ P3 eff P total = 850 + 4581.27 + 1058 P total = 6489.27 W If V1 went open circuit, calculate the new value of neutral current for Figure1. if V1 went open or is at fault then I1 will become zero and the neutral current will be the sum of the other two currents I1 and I2 IN = I1 + I2 + I3 V1 went open so, I1 = 0 therefore, IN = 0 + I2 + I3 IN = I2 + I3 IN = (0 +j 23) + (-9.2 +j 0) IN = (0 9.2) + j (23 + 0) IN = (-9.2 + j23) A (Rectangular Form) IN = 24.77 111.80 A (Polar Form) Single-core Three-Phase Double-Wound Transformer Introduction: Transformer is a static device which transfers electrical energy or power between two or more than two circuits using phenomena of Electromagnetic induction. It takes the current of one voltage and converts it into a different voltage. The amount of transferred energy from Primary circuit to the Secondary Circuit is equal, and the losses are ignored. The frequency of the circuits does not change but the voltage and current of each of the individual circuit is changed, it is increased or decreased, unless we use the transformer as a one-to-one isolating transformer. Basically, the transformer perform the function of changing electricity from high to low voltage by making use of the following properties of electricity. Magnetism is always present around in an electric circuit. Magnetic field is always changed by changing the strength or moving the conductor therefore voltage is induced. Voltage is known as the measure of the Force or Pressure that is used to push the electrons around the circuit. Electricity at a higher voltage goes in the transformer and runs through the large number of coils that are wounded around the iron core. As the current is changing, the core magnetism will also be changing. A wire with less coils around the iron core is known as the output wire and the changing magnetism produces current in the wire. When the number of coils are less that means less voltage and more coils means more voltage. Therefore, the voltage is either stepped down or stepped up according to the number of coils in the wire. A common transformer involves a ferromagnetic core which ensures that values of magnetic flux linkage remain high. But there are some factors related to the ferromagnetic materials that are responsible for part of the loss associated with power transfer. These losses are as follows: 1. Core losses: Core losses can be classified as the sum of eddy currents losses and the hysteresis loss. Hysteresis loss: Energy that a magnetic material soaks in cannot be recovered completely. Core of the material is excited by an A.C source, the flux density rises and falls with the magnetic field strength or current which is basically sinusoidal. When the magnetizing current increases the flux density also increases but there comes a point after which if there is any further increase in the current, flux density is saturated. If the current is reduced from the saturation point to zero, flux density will start to decrease. When the value of the current reaches upto zero the flux density should also become zero but it does not become equal to zero. Some of the flux density will still be present in the material for the zero current, which is called as a residual magnetic flux. Thus, the total amount of energy used to magnetize the material cannot be recovered back and this energy is trapped within the material core and is dissipated as a form of heat. Area of B/H curve gives the hysteresis loss, larger the loop the greater the energy required to create the magnetic field. Eddy current losses: If a coil is wrapped around a core made up of some material and an A.C source is applied to circuit, eddy current losses take place. As the supply to the coil is changing or alternating which produces an alternating flux in the coil. The varying flux in the core induces e.m.f in the core material due to which eddy currents start to flowing in the core material. Therefore, the energy is lost or dissipated in the form of heat because of eddy currents. The laminations in the core can reduce the eddy current losses. Thin sheet steels which are separated from each other must be used because these insulated sheets reduce the amount of the current flow and hence the eddy current losses. 2. Copper losses: Copper loss occurs when the transformer is loaded, the input power is dissipated as heat in the primary and secondary windings of the transformer because these windings have internal resistance. When the load is low, the amount of heat produced is small but at high loads the amount of heat produced becomes significant. à ¯Ã¢â‚¬Å¡Ã‚ · Construction of Single-core three-phase double wound Transformer: A single-core three-phase double wound transformer consists of three sets of primary and secondary windings, individual set winded on each leg of the core made up of iron. The windings consists of turns made up with the insulated wire. These coils are then mounted on a magnetic core material in such a way that the magnetic flux produced by one coil increases and ensures that the most of the magnetic flux links with the second coil so that mutual induction is being increased. The coils are spaced 120 degrees apart. The transformer is filled with a dielectric oil and thus provide insulation in-between the winding and case. These windings are either connected in star or delta configurations. Delta Connection: Delta system proves excellent for distribution system for short distances. These types of transformers are used in neighbourhood and commercial loads of small magnitude near to the substations. There is one kind of voltage present between the 2 wires in the delta system. This system is shown by a Triangle. The voltage between any two wires will be the same and from each individual point of the Triangle, wire emerges which represents a three phase. Star Connections: For a star connection, voltage of two lines is the same as the voltage on a 3 phase system. In Star connection, each of the windings are made up connecting each individual winding end to end and this point is the star point or neutral point of connection winding. Connection for neutral and 3 phase connections are then taken out of transformer. à ¯Ã¢â‚¬Å¡Ã‚ · Applications of Transformers: Transformers in Electrical Engineering: An electrical engineer may put a transformer in a circuit for many reasons. If the device being powered require higher power than what is available locally or the powered device needs frequency matching, a transformer is placed in such circuits. For example signal and audio transformers are used to couple amplifiers and microphones to the input of the amplifiers. Power Utilities: When driving through a rural area, power polls and overhead power lines can be seen and transformers are placed on these power polls by power utilities. Utility substations make use of transformers to deliver power of certain usable level and quality to consumers and businesses. Power Generation and Distribution: Electrical power is generated at the power station and this electrical energy is then transferred to the consumers through high tension power lines. To distribute the electricity from the power station to the consumer, different transformers are used in stepping up and stepping down the voltage up to the certain level. Commercial use: Every electrical device uses transformer in one way or another. Almost every commercial building has at least three or four large high power transformers in order to provide required voltages to operate overhead lightning system, telephone system, heating, operating electrical equipment in labs and much more. Transformers in home: There are a lot of transformers used in many appliances at our homes that require different voltages for their operation. Electric appliances like dishwasher, washing machine, microwave and fridge require comparatively high voltages between 110 and 240 volts, the devices like laptops and charger mobile phones and MP3 players require relatively low voltages. A laptop charger requires up to 15V while mobile phone charger requires up to 6V and M3 chargers require up to 12V to charge up their batteries. Thus, these appliances have small transformers built in them which convert the domestic supply of 110-240 volts into a low voltage that they require for their operation. à ¯Ã¢â‚¬Å¡Ã‚ · Power Transmission and Distribution System: Three-phase system is used in power transmission because less amount of conductor is used to transmit electrical energy to different places. Three conductors carry 3 alternating currents peak values of which reach at different intervals of time. If a conductor is taken as a reference point, there is a delay of time by one third and two third of a cycle of the current for the remaining two currents. Because of this delay in the available phases, constant power is transferred over each cycle of current. There can or cannot be a neutral wire in three-phase systems. Neutral wire is used to allow a higher voltage while still supporting the appliances operating at lower single phase voltages. As loads can directly be connected between the phases so there is no neutral current wire in high voltage distribution. There are many factors that make three-phase system very desirable and reliable in electric power systems. In a load which is linearly balanced, the phase currents cancel each other and add up to give a zero which also helps in eliminating the neutral wire. Phase conductor carry same amount of current which means that they all can have a same size of conductor for balanced conditions. Moreover, the transfer of power in the system is constant for a linear system, it reduces the vibrations in a system. à ¯Ã¢â‚¬Å¡Ã‚ · Generation: Electricity is generated at the power station at around 10kV by rotating a coil in the magnetic field. In power stations, all the generators are synchronised so that they all produce electricity that oscillates together. For more efficient generation, three windings are used on the generator to produce three-phase electricity. Sources for power generation: For distribution, the following types of resources are available for the generation of the electricity. Conventional Methods: Thermal energy: Thermal energy or the Nuclear energy is used to produce steam for the turbines that drives the rotating AC generators to produce electrical energy. Hydro-electric: Potential of water is stored at a higher altitude and is made passed through the turbines which in turn drive the generators. Non-Conventional Methods: Wind power: Winds blowing at high speeds are used to drive the turbines that are coupled to the rotating AC generators. à ¯Ã¢â‚¬Å¡Ã‚ · Transmission: Transmission has an important role between the production of power and the usage of power. Transmission lines carry high voltage electricity over long distances from power plants to the consumers. Once the power is generated. It is send to the substation in the power plant where the voltage is stepped-up using step up transformer for transmission purposes. When the voltage is stepped up, it helps in the reduction of the transmission losses. It is then sent to the grid station from where it is further transmitted to different cities. Why there is a need to step up the voltage for transmission: For transmission over long distances, transmission lines are made up of conducting materials like aluminium and power loss is always associated with these conducting materials. This is because if the current through the wire is I and the resistance of the wire is R then an amount of electrical power I2R is dissipated as heat. This will result in a much less power at the receiving end than the actual power generated at the station. Thus, when power is transmitted at a high voltage, wires of low current carrying capacity are used so there is no need of thick wires that cost considerably high instead they can be replaced by thin wires that cost less. à ¯Ã¢â‚¬Å¡Ã‚ · Distribution: Substations reduce the voltage of the electricity from the transmission lines. The power grid is connected to the different parts of the country and it distributes the power in different cities through transmission lines. The transmitted power from the power grid is stepped-down to 110,000 volts from 230,000 volts using a step-down auto transformer. Then for the distribution of power for industrial uses, the power is again stepped-down to 11,000 volts from 110.000 volts by step-down transformer located in the streets. This reduction in the voltage increases the current in the wires and thus the losses but greatly reduces the cost of power poles and increases the safety. The distribution substation further reduces the voltage to 230 volts or 440 volts for the local transmission for domestic purposes depending upon the need of the user. Some business and houses require two or three-phase power supply while the others only need single phase supply. à ¯Ã¢â‚¬Å¡Ã‚ · Operation of the transformer: Transformer works on the principle of mutual induction. According to Faradays Law of electromagnetic induction: Rate of change of flux linkage is directly proportion to the induced emf in a conductor or coil with respect to time. When primary winding is connected to a voltage source, an AC flows through it and which produces a continually changing magnetic flux that surrounds the winding. This changing magnetic flux flows to the secondary winding as some flux from primary winding will be linked to the secondary winding. As magnitude and direction of the flux is continually alternating, change of flux takes place in the secondary winding. According to Faradays law of electromagnetic induction, this changing magnetic flux produces an induced electro motive force or simply the voltage in the secondary winding of transformer therefore, a current start to flow if the circuit is closed. The rate at which the flux changes depends upon the amount of the flux which is linked with the secondary winding of the transformer. Therefore, it is important to link all the flux from the primary winding to the secondary winding of the transformer. It can be done by putting a low reluctance path which is usually common to both of the windings and that low reluctance path is known as the core of the transformer. Three-phase Induction Motor Introduction: Electric motor is a device which performs the operation of converting electrical energy into a mechanical energy. The induction motor is known as a three-phase AC motor which is widely used in the industrial applications as they are: Self-starting. Their construction is simple and compact. Less expensive. Require minimum amount of maintenance. More reliable and highly efficient. Additional starting motor is not required and do not required to be synchronised. Induction motor is also known as asynchronous motor. Due to inductive coupling, the generated electromagnetic power is transferred to the secondary winding. These windings are being separated by air gap between them. The induction motor consists of a Stator and a Rotor. The motor frame is permanently attached with windings of very low resistance. When current and voltage is applied to the terminals of Stator windings, a magnetic field is produced. à ¯Ã¢â‚¬Å¡Ã‚ · Applications of three-phase induction motor: Induction motors are most demanded motors in the industry. Some of their applications are given below: Industrial drives make use of 3 phase cage rotor motors because they are pretty simple, efficient and are not costly. Single phase induction motors are used where the load is comparatively smaller. These motors are being

Psy 322 Week 1 Assignment Essay

How do people measure, or know or how goods will be accepted? Consumer psychology is how people relate to the goods and services they use in their daily lives. Consumer psychology studies people and by doing so provides what factors are important in the decision making of purchases and the value of services. By having this knowledge of consumer’s organizations, businesses and retailers improve their marketing. First of all there needs to be an understanding of why the consumer buys in the first place. Is it for a need or a want or is it to fulfill something? The buying process can be very basic or very complex and have many influences from external to internal reasoning. There are many things that factor in to understanding the entire process and the best way to understand them is through consumer psychology. Decisions to buy can be emotional. Emotions can lead a person to shop. Feelings are people’s primary way to make judgments and decision making. A woman can be upse t at her husband, need a break from the kids, or she could be happy and want to spend impulsively. A marketer only has a chance to contend with commercials and ads to penetrate the feelings of the consumer. Consumer personal behavior is influenced by many, family, culture, environment, competition and social attitudes. These are factors to be evaluated and how they are used for persuasion. Friends and family influence the clothes one wears. Culture and family are a persons or peoples area of up bring that can influences the way services are done and the way products are purchased. After taking a deeper look into the whole idea of consumer psychology there are lot of new approaches that are on the horizon that could possibly take effect. Image is a factor into today’s society whether we believe it or not. There is always the clichà © that â€Å"size doesn’t matter† but in all honesty people are always trying to find a way to become healthier. Well according to the New York Times grocery stores have thought of an idea to get people to have realization while walking the stores by putting mirrors in the shopping cart that will allow them to get a glance of themselves before consumers chose to put junk food in the cart. Marketers feel it might help them to reconsider groceries if they have to take a good at themselves before putting their items in the cart then maybe wiser decisions will be made. Another area that has changed psychological views of consumers is the economy. We have been in a recession for quite some time and have seen that people aren’t going out and buying as much. In an article known as â€Å"From buy, buy to bye-bye: The recession will have a lasting impact on the way people shop† there is much indication that in many different areas those sales have plummeted and continue to do so. The consumer psychological view is to save money and prices of any type of sales keep rising without any le-way for the consumer. If marketers do not learn make bargains for their consumers’ bucks then there will be a better chance for the economy to buy instead of saying bye-bye to buying. All in all, the consumer is looking for options that will help them in their lives to better themselves. Although sometimes the mechanism that marketers use to persuades the consumer to make choices that are more convenient and might not be as good for them. Consumer psychology is at a very vulnerable state in today’s society because everyone wants to be a part of something big or new that is how the market communicates with them. Therefore the understanding is that sometimes consumers have no hope in area of choice because the market is always there to persuade them to try new things. REFERENCES: MOSS, MICHAEL. Copyright 2013. Nudged to the Produce Aisle by a Look in the Mirror Retrieved from http://www.nytimes.com/2013/08/28/dining/wooing-us-down-the-produce-aisle.html?_r=0 The Economist. Copyright 2009. From buy, buy to bye-bye: The recession will have a lasting impact on the way people shop. Retrieved from, http://www.economist.com/node/13415207

The Ultimate Apush Essay Samples Trick

The Ultimate Apush Essay Samples Trick College Board sample essay sets are a terrific method to test how well you comprehend the rubric. An official letter follows a right format that's used in every business application. If you're searching for some expository essay samples, have a look at some tips here below and don't hesitate to use them while writing. Essay pages can be full of fluff, and an easy thesis and analyzing a couple documents may get them a few points. Apush Essay Samples - Is it a Scam? For the reason, it's better to practice writing short essays. Whether you need to make a paper of special flawlessness, just purchase an essay here and our writers will provide help. You may receive a very good sense of what sort of writing goes into a high-quality essay. Helpinessayscom is a preeminent customized history essay writing website where you are able to employ a professional history essay writer at reasonable rates. At our essay support, essays are always delivered in a brief moment. It's going to prepare the full essay. The other essays will help give you an awareness of what score your essay may have gotten that year and any areas you might have overlooked. Writing an APUSH essay turns out to be difficult because of absence of time. Making connections is particularly important if it regards the rebuttal for your argument. Formal letter example for students is a fundamental thing. The response to this question is dependent on your study plans! In reality, if a student is following the sample he or she'd have the ability to compose an expert vacation request letter with the assistance of a sample or a template. The Pain of Apush Essay Samples Students should be careful to leave themselves enough room to deal with all 3 parts on the 23-line page. Men and women say they cost too much for the grade of the product while some are excited about all its features. They think they cost too su ch for the grade of the product (Sideman). Imagine the simplicity and convenience of having all your kilts and accessories in 1 place. You're going to be surrounded by writing professionals throughout the plan of order placement, and once you opt to purchase essay and select an allocated writer, things will get even more exciting. Students that are good with the online order their own books without needing to manage the bookstore (Robertson). Experts also feel there are so many advantages from the E-book that there isn't any reason to even own printed books (E-books). Begin by reading through both prompt alternatives, and select the one which you feel more confident in writing about. Taking an exam is an arduous task that needs a prior preparation and a quite a very long education practice. You can't pass this kind of exam in general without preparation and detailed knowledge in the area of the U.S. History. Students need practice within this time crunch. Many students ma y wish to spend plenty of time planning and writing that they'll not have on exam day. The Ideal Strategy to Apush Essay Samples Don't be scared to talk about your ideas as part of creative procedure and remember there's just one approach to reach the desired goals receiving papers which have been meticulously checked, reviewed and proofread. The enabling objectives to find the research goal are the next. You'll know that you have to work on your thesis abilities. This research highlights over the significance of art in our everyday life it also recalls us about the many types of art and the way every one of them depends on special. Fortunately there are a number of basic rules you may follow to ensure. Needless to say, this list isn't exhaustive, these are only a few examples of the most well-known reasons students turn to writing services. As you know by this time, reviewing different students' work can be a rather powerful and beneficial approach to study for DBQ. You s hould work on recognizing what constitutes historical context in line with the AP. The University of Michigan is starting to visit a digital reading system rather than print which will also be helpful for the E-book (Glazer). The previous scores as awarded by the College Board will be useful in establishing a ballparkobviously a 9 is still likely to be an excellent essay under the 7-point scalebut there could be some modest differences in grades between the 2 scales. Also have a look at her review of the ideal AP US History textbooks! Apush Essay Samples Features The topic question is going to be related to a specific process particularly moment. One of the most frequent mistakes is that students do not stay in the time frame. If you don't feel just like you have the time to write essays by yourself, we will give you a hand, any instance of the day, seven days per week. Thus, you'll have a feeling of time and will be in a position to write more for a briefer period of time. After you locate a service you prefer, don't neglect to look at my review of it. It' s vital that the service you decide on knows for sure they're only selecting the ideal essay writers. In a nutshell, the service exists, so should you need to use it in order to find a top essay, that's reason enough. If these aren't present, then you need to consider an alternate support.

American Obesity - Free Essay Example

Sample details Pages: 9 Words: 2680 Downloads: 6 Date added: 2019/03/22 Category Health Essay Level High school Tags: Obesity Essay Obesity in America Essay Did you like this example? Abstract As a Nutrition major, I have always wondered, Why is it that in the last few decades, people around the world have been increasing in weight, especially in America? From 1990 to 2018, American obesity has grown from being 11% of the population to 35% (The State of Obesity). Why do some people have such a hard time losing weight, while others have to work really hard to even gain a few pounds? So, what exactly is obesity? Obesity is defined as having a BMI (Body Mass Index) over 30, and is considered a chronic disease that increases the risk of a variety of health conditions. This includes, but is not limited to: insulin resistance, diabetes, high blood pressure, gallstones, stroke, heart attack, osteoarthritis, and even cancer (Balentine).. Don’t waste time! Our writers will create an original "American Obesity" essay for you Create order The location of fat on the body can increase these risks; generally, more abdominal fat means a higher risk. Storing fat in the abdomen is known as an apple shape, while storing fat in the hips and legs is a pear shape. The waist to hip ratio, which is found by dividing the measurement of the smallest part of your waist by that of widest part of your hips, is used to assess the increased risk of obesity related diseases. If the ratio is greater than or equal to 0.8 for women or 1.0 for men, their risk for obesity related diseases is elevated (Balentine). In order to understand this obesity epidemic, we must first understand what causes obesity in the first place. Although there is definitely an influence from peoples personal actions, it turns out obesity is not purely a consequence of an individuals choices; there are genetically predetermined factors that impact ones likelihood of gaining weight. One study used identical twins to test if genetics play a role in ones weight and fat distribution. Twelve pairs of twins were given a one thousand calorie a day surplus over the course of one hundred days for six days per week. It turns out each twins weight gain and fat distribution was similar within pairs, but varied between the twelve different sets (Bouchard). These findings are very significant, because they demonstrate just how much ones body composition, location of fat distribution, and metabolic rate can vary based on genetics. Ones ethnicity, gender, hormone levels, and childhood weight, all of which are influenced by genetics, play a role in the likelihood of becoming obese. African Americans and Hispanics, women especially, have a tendency to put on more weight earlier in life; this is most likely a result of differences among cultures relating to food. People who are overweight in their 20s have a higher chance of becoming obese in their late 30s. Generally, the earlier the person is overweight in their life, the more likely they will become obese later on. Women are more likely to become obese because of their tendency to put on more weight due to hormones such as estrogen (Balentine). Although heredity does play a significant role, the foods people eat in America have a great impact on obesity. Lots of sugary, calorie dense, man-made junk foods are marketed to the public, and sometimes they can be very hard to resist. The low nutrient profile in these foods makes people feel full less quickly, often causing them to overeat, filling up on too many calories and not enough protein, fat, or complex carbohydrates (Gunnars). The aggressive marketing of junk food companies does not help either. Advertising for many junk food items is aimed towards children, who do not yet have enough knowledge to make conscious, informed decisions about what they eat, and they get addicted to sugar at a young age. Countless digital marketing ads are portrayed through phones, games, and social media to children and adolescents. In 2008, the food industry spent about $10 billion per year in marketing to children, according to the Federal Trade Commission (Toxic Food Environment). Certain junk food products are advertised as being healthy, with labeling that claims they are beneficial to the body in some way, when in reality they are not healthy. Many companies slap labels on their products such as all natural, multigrain, sugar free, fat free, light, among many others (16 Most Misleading Food Labels). These claims can even trick adults into thinking that they are buying a healthy product (Gunnars). For example, cereals such as Honey Nut Cheerios may claim that they are whole grain, low fat, contain all 12 vitamins and minerals, are a good source of iron and calcium, and that they may reduce the risk of heart disease and lower cholesterol (Honey Nut Cheerios | Gluten Free Oat Cereal), but they are still high in sugar and have little protein per serving. Children must be taught at a young age about the importance of fruits and vegetables in the diet, and to limit sugary items. As a result of consuming so many high sugar, calorie dense foods, people can develop insulin resistance. Insulin is a hormone in the body that regulates the conversion of energy into fat versus being utilized elsewhere in the body. In a person who is insulin resistant, the body does not register when enough of the hormone has been made, and continues making more of it; this causes more energy to be stored as fat instead of used by the body. In order to prevent high insulin levels or insulin resistance, one must not eat an excessive amount of refined carbohydrates and have a good amount of fiber (Gunnars). People can also become resistant to the hormone leptin, another possible cause of weight gain. Leptin is responsible for reducing appetite when the body has a sufficient amount of fat stored. However, in obese individuals, leptin cannot be registered by the brain because it is unable to cross the blood-brain barrier. This results in an unsatiated appetite, even with plenty of fat storage. Leptin resistance is the most common initiator of fat and weight gain that causes individuals to become obese (Gunnars). The environment in which people live and work greatly impacts what they eat, and in turn, the likelihood of becoming obese. This includes both physical and social surroundings, such as living as a family, being at work or school, and where a person lives (Toxic Food Environment). Families influence the way their children eat in several ways. The foods provided at home impact what children will like as adults. Eating together as a family influences a healthier diet for the child if the parents provide fruits and vegetables at the dinner table. However, some low income families cannot afford to buy healthier foods such a fruits, vegetables, and whole grains, and the unhealthier options such as pre-made meals are much cheaper and convenient. Many low income parents are single, working full time, and do not have the time to cook healthy meals (Toxic Food Environment). The workplace of adults also has an effect on food choices and likeliness to gain weight. Usually, unhealthy options from vending machines, or the huge box of donuts a co-worker brought in, are readily available to be consumed. Stress and fatigue from too much work can also cause people to exercise less and work more, which leads to less calories being burned and potential weight gain (Toxic Food Environment). While the workplace environment affects the diets of adults, the same goes for children in school. Many schools, albeit having a National School Lunch program, do not have the healthiest choices for kids. Junks foods are sold outside the National School Lunch program, making them known as competitive food. These may include chips, candy, and sugary drinks that many kids are drawn towards (Toxic Food Environment). The neighborhood where one lives also affects the accessibility of food. Many people, mostly low-income families, are located in food deserts, or areas with limited access to supermarkets. Instead, they have greater access to convenience stores, which usually do not have as much variety as supermarkets and contain mostly processed foods (Toxic Food Environment). This leads to people in food deserts having less nutrient dense diets. There is a great need for healthier options to be accessible to everyone. Another factor that could be contributing to the obesity epidemic is the way our society treats obese people. There has long been a stigma that people who are obese are lazy, unmotivated, and careless. But this is not always the truth. Putting down obese people only makes them feel badly about themselves and exacerbates the problem. A study done by Brenda Major and others demonstrates the effects of such a weight stigma on women. Women were randomly selected to read an article that was either related to weight stigma or something completely unrelated. Overall, the women who were exposed to the weight stigma article felt worse about themselves and were therefore less motivated to make changes. In particular, it made women who felt they were overweight consume more calories. So, weight stigma is not motivating people to change themselves, but only making them feel more hopeless. The weight stigma is also evident in the health care system. Many doctors are guilty of not taking their obese patients seriously when they have a problem, assuming they just need to lose weight to feel better. Take for example, Sarah Bramblettes experience with a doctor when she started experiencing hip pain. Sarah was over four hundred pounds, and when the doctor came to assess her hip issue, he said, Let me cut to the chase. You need to lose weight. Without any further examination other than her physical appearance, he wrote down on her list of symptoms obesity pain. Sarah was dumbfounded. She made an appointment with another doctor, one who actually diagnosed her, and discovered she had a scoliosis progression (Kolata, Why Do Obese Get Worse Care?). A study performed in 2001 at the Texas Medical Center of Houston provided evidence that doctors do not treat overweight and obese individuals the same as patients who are not. 122 physicians were evaluated on how they treated average weight, overweight, or obese patients, all of whom had the same ailment. The results were that the physicians spent less overall time with the overweight and obese patients than the average weight ones (Hebl). With obesity rates continually growing, physicians need to change the way they view obese or overweight individuals, and start taking their needs as seriously as any other patients. Additional problems affect the quality of medical treatment obese people receive. One of these problems is that there are no calculated dosages of medication for obese people. All of the dosage guidelines are assumed for people at a healthy weight. Another is that the majority of MRIs are not large enough to contain an obese person, forcing doctors to have to give up the diagnosis. Lastly, many procedures are not done on obese people. For example, surgeons are not willing to perform knee surgeries on people with a BMI over 40. This is because working on heavier individuals increases the chance of a surgical complication, and doctors dont want to risk a negative effect on their surgical success rate. This situation is not ideal when the majority of people with joint problems are overweight or obese. All of these roadblocks to treatment are not fair for obese people, and changes must be made to accommodate their needs (Kolata,Why Do Obese Get Worse Care?). Despite the bad rap obesity has for increasing the risk of certain health implications, it is actually possible for a person to be classified as obese and still be metabolically healthy. In other words, their metabolism, or the rate the body burns calories through the chemical processes that occur within, is at a normal, healthy rate. These individuals are defined as MHO, or Metabolically Healthy Obese. One possibility of being considered MHO is if your BMI is above 30, but you are muscular and physically fit. Positive lifestyle habits, such as a nutrient rich diet, exercise, not smoking, and a moderate consumption of alcohol can play a role in a persons categorization as metabolically healthy obese. Currently, there are no specific criteria for classifying MHO. Some possible ways to determine MHO could include ones waist circumference, blood pressure, cholesterol, and blood sugar levels, insulin resistance, and physical fitness. Approximately thirty-five percent of obese people are classified as MHO (Nordqvist). This is quite a lot of the obese population, so it would be important to know how to distinguish the difference between the metabolically healthy and the metabolically unhealthy. Such knowledge could result in a better understanding of how to treat obesity. The way many obese people approach weight loss is another issue with the obesity epidemic. It is common for people to lose weight too quickly, as can be seen on the television show Americas Biggest Loser. Kevin Hall, Senior Investigator at the National Institute of Health in Washington, was interested in seeing what happened to the Season 8 contestants post show. Hall monitored their weight and metabolic rate for 6 years after the end of the show, and the results were shocking. Most of the contestants had gained back much of their original weight, some even more. Not only that, but their metabolisms were slower than when they first started (Kolata, After the Biggest Loser). Danny Cahill, the winner of Season 8, lost a whopping 239 pounds, going from 430 pounds down to 191. However, in the years after the contest, the pounds came back rather quickly. After the six-year study, Danny had gained back 100 of the pounds he had lost, ending at 295 pounds with a decreased metabolism, burning about 800 calories less than the average person his weight. Why, after all his hard work, did the pounds just pile back on? (Kolata, After the Biggest Loser) It seems that Dannys body is fighting back against the damage he has done by losing an extreme amount of weight in a short period of time. The more successful you are at losing weight, the slower your metabolism will be, and the more hungry youll be, says Hall. As Danny lost weight, his metabolism decreased, making it very difficult to maintain the final weight he achieved. Levels of the hormone leptin, responsible for controlling hunger, also decreased, making Danny feel extremely hungry on the low calorie diet that was necessary to maintain his new weight. To avoid feeling constantly hungry, Danny had to eat more food. But, with such a lowered metabolic rate, his body could not maintain his new weight, so he continued to put on more pounds (Kolata, Biggest Loser). Its like asking someone to hold their breath, you can do it for awhile, but its very difficult to do it for much longer than a minute or two, Hall explains. Some scientists believe the body goes through a famine mechanism, in which the body responds to rapid weight loss by reducing metabolic rate and leptin levels in an attempt to hold onto and put back on as much weight as possible to return the body to homeostasis. The body reacts as if it were in an extreme crisis with limited availability of food, lowering the metabolic rate and leptin levels as a mechanism of survival (Kolata, Biggest Loser). The metabolisms of the Biggest Loser contestants had no time to adjust to the extreme caloric deficit they experienced. Rebecca and Daniel Wright, two other Biggest Loser contestants who also gained weight back post show, have a new plan of action to keep the weight off for good. Instead of dramatically reducing calories right away, they are gradually reducing the number of calories they eat per day. This way, their bodies are adjusting slowly to the change in diet without registering it as as a threat to survival. Besides a gradual decrease in calories, other advice for successful weight loss recommended by Susan Biali, M.D., is to avoid extreme dieting, enjoy the foods you eat, and make realistic changes you know you can make a part of your lifestyle. Extreme dieting, like what was done on Americas Biggest Loser, has a yo-yo effect, and is not sustainable. It only promotes stress and deprivation, and makes the dieter feel as if they failed.