A.C. Devices Essay Example for Free

A.C. Devices Essay INTRODUCTION Although in our daily life we use A.C. current devices. But rectifier is a ‘Electronic device which converts A.C. power into D.C. power’. The study of the junction diode characteristics reveals that the junction diode offers a low resistance path, when forward biased, and a high resistance path, when reverse biased. This feature of the junction diode enables it to be used as a rectifier. The alternating signals provides opposite kind of biased voltage at the junction after each half-cycle. If the junction is forward biased in the first half-cycle, its gets reverse biased in the second half. It results in the flow of forward current in one direction only and thus the signal gets rectified. In other words, we can say, when an alternating e.m.f. signal is applied across a junction diode, it will conduct only during those alternate half cycles, which biased it in forward direction. TYPE OF RECTIFIER Mainly we have two types of rectifier : 1. Half wave rectifier. 2. Full wave rectifier. JUNCTION DIODE AS HALF WAVE RECTIFIER When a single diode is used as a rectifier, the rectification of only one-half of the A.C. wave form takes place. Such a rectification is called half-wave rectification. The circuit diagram for a half-wave rectifier is shown in Fig. Principle : It is based upon the principle that junction diode offers low resistance path when forward biased, and high resistance when reverse biased. Arrangement :- The A.C. supply is applied across the primary coil(P) of a step down transformer. The secondary coil(S) of the transformer is connected to the junction diode and a load resistance RL. The out put D.C. voltage is obtained across the load resistance(RL) Theory : Suppose that during the first half of the input cycle, the junction diode gets forward biased the conventional current will flow in the direction of the arrow-heads. The upper end of RL will be at positive potential w.r.t. the lower end. During the negative half cycle of the input a.c. voltage, the diode is reverse biased. No current flows in the circuit, and therefore, no voltage is developed across (RL). Since only the positive half cycle of the input appears across the load, the a.c. input is converted into pulsating direct current (d.c.). Disadvantage of Half-Wave-Rectifier : 1. Half wave rectification involves a lot of wastage of energy and hence it is not preferred. 2. A small current flows during reverse bias due to minority charge carriers. As the output across (RL) is negligible. 3. The resulting d.c. voltage is not steady enough for some purpose. The following device is used when a very steady d.c. voltage is required. JUNCTION DIODE AS A FULL WAVE RECTIFIER â€Å"A rectifier which rectifies both waves of the a.c. input is called a full wave rectifier†. Principle :- It is based upon the principle that a junction diode offers low resistance during forward biased and high resistance, when reverse biased. Difference from half-wave-rectifier :- The main difference is that in full wave rectifier we use two diodes. For this when we apply a.c. current to the rectifier then the first half wave get forward biased due to first diode. And when the second half wave comes. Then at that time the second diode comes in action and gets forward biased. Thus output obtained during both the half cycles of the a.c. input Arrangement :- The a.c. supply is applied across the primary coil(P) of a step down transformer. The two diodes of the secondary coil(S) of the transformer are connected to the P-sections of the junction diodes (D1) and (D2). A load resistance (RL) is connected across the n-sections of the two diodes and at centre of the secondary coil. The d.c. output will be obtained across the load resistance (RL). Theory :- Suppose that during first half of the input cycle, upper end of (S) coil is at positive potential. And lower end is at negative potential. The junction diode (D1) gets forward biased, while the diode. (D2) get reverse biased. When the second half of the input cycle comes, the situation will be exactly reverse. Now the junction diode (D2) will conduct. Since the current during both the half cycles flows from right to left through the load resistance (RL) the output during both the half cycles will be of same nature. Thus, in a full wave rectifier, the output is continuous but pulsating in nature. However it can be made smooth by using a filter circuit. REVERSE BIASING ON A JUNCTION DIODE A P-n junction is said to be reverse biased if the positive terminal of the external battery B is connected to n-side and the negative terminal to p-side of the p-n junction. In reverse biasing, the reverse bias voltage supports the potential barrier VB. (Now the majority carriers are pulled away from the junction and the depletion region become thick. There is no conduction across the junction due to majority carriers. However, a few minority carriers (holes in n-section and electrons in p-section) of p-n Junction diode cross the junction after being accelerated by high reverse bias voltage. Since the large increase in reverse voltage shows small increase in reverse current, hence, the resistance of p-n junction is high to the flow of current when reverse biased. MATERIAL REQUIRED 1. Transformer : It is device which is used to increase or decrease the alternating current and alternating voltage. For the rectifier, it may be step down or step up. 2. Junction Diode : It is made up of p-type and n-type semiconductor which conducts when the p terminal of diode to connect to positive terminal of battery and n region is connected to negative terminal of battery i.e. during forward biased and does not conduct during reverse biased.

Educating Rita by Willy Russell Essay -- Educating Rita Sociology Soci

Educating Rita by Willy Russell "Educating Rita" displays the major changes that occur in the main character, an initially narrow minded, outspoken and socially naà ¯ve Liverpudlian trapped by her working class life. Rita thinks an increase in intelligence and worldly knowledge will change this, and set her "free". She strives to change classes, and although is different from her working class peers, she still isn't ready to be accepted as middle class. She aims to reach her goal through an Open University course, yet naively thinks knowing what books to read and clothes to wear will allow her to immediately become accepted as part of her chosen social strata. Change is a major part of the play, affecting Rita in both positive and negative ways. It shows how the influence of education helps to bring about these changes, and how eventually Rita is able to overcome and negative problems and settle on a happy balance. Rita is also molded by her tutor, Frank, and learns a great deal from him, whilst also teaching him in many ways. Rita's bright, bold, bubbly character is revealed in the very first scene, as the two characters are introduced. She makes a very dramatic entrance, bursting through the door, swearing, and immediately drawing all attention to her. She isn't really sure how to act, and her insecurity and nerves make her appear in such a loud manner. This shows how little she understands of formal interview situations- one would expect her to appear fairly meekly, maybe shy, and also very formally, yet she acts cheekily and informally. For example, not only does she ask Frank if she can smoke, but she also gets out her cigarettes before he has had a chance to answer. She even offers him one, trying... ...re introduced, including maturity. In the middle of the play, she thinks Frank is a bad teacher, but by the end, she realises that he made all this possible for her, and her maturity means she isn't too stubborn to thank Frank and truly appreciate what he has done for her. Although she changed in negative ways, she learnt from these. She realises that she doesn't want to risk becoming trapped again, like with Denny, but wants to dictate her own destiny with the choices she makes. The ending is left very open, not telling the theatre viewers what happens to either Rita or Frank, but lets you imagine for yourself what paths they take and where and how they live their lives. This reflects the theme of choice, by letting viewers decide what happens, but also for the characters to decide and change which way they will go and what choices they will make.

Psycho Analysis

ysisPsycho Final Analysis Joel Schain Film and Literature Period 3 10/2/12 Alfred Hitchcock’s Psycho has been ranked as one of the top 10 best horror/suspense films of all time because of his unique way of filmmaking. Some of the many significant cinematic elements uses include internal diegetic sound, and dissolving. Internal diegetic sound was used throughout Hitchcock’s Psycho to create the illusion that Norman Bate’s mother was still alive. Only at the very end of the film do you find out what really happened to Norman’s mother, and throughout the film the audience is wondering when they will get to match the voice with her face.The internal diegetic sound appears to be Norman’s mother talking to him, when really it’s just him talking to himself. This effect leads the viewer to think that Norman’s mother is this unstable, controlling, psycho murderer when really it’s Norman all along and he just can’t accept the fact that she’s really gone. In the last scene Norman is asked a question in his prison cell and the voice of his mother replies, indicating that the mother part of him has consumed his personality.Another important cinematic element used in Psycho is the dissolve editing technique. At the very end of the film when Norman Bates is sitting in his prison cell, he slowing lifts up his head and grins, then it slowly dissolves into the face of his dead mother’s corpse, showing the viewers that they are now one. The question you find yourself asking throughout the film is, â€Å"Who is the murderer? † That question is answered at the very end when Norman and his mother dissolve into one face, proving that Norman was the crazy one all along. Psycho Analysis The Shower Scene from Alfred Hitchcock’s Psycho is a crucial scene in the plot of the film. The scene itself shows the death of the main Protagonist, Marion. In this essay I am going to explore the Shower Scene in detail and show how Alfred Hitchcock created the excitement present in the scene as much by Technique as by Action and I will show how the scene is so important to Psycho as a whole. Perhaps the most distinguishing feature of Psycho is the score to the Shower Scene. The composer accountable for it is Bernard Herrmann. The Action of the scene is very fast-paced and the Music present in the scene is a direct reflection of this. The instruments present all belong to the String family; Cello, Violin, Viola and the Double Bass are all present in the Scene. This creates a very peculiar sound, no Brass instruments to create the usual ‘Noise’ affiliated with action and no Woodwind to soften the sound and calm things down. The sound is very rough, the high, screeching Violins create excitement as the action becomes more frenzied, so do the Violins. Each knife blow is accompanied by ‘screams’ by the high violins. This goes on for the duration of the attack, there is no relent until Marion is dead. This leaves the Audience lost, confused as to what exactly is going on in front of their eyes. The screaming emitted from Marion and the Violins is almost in-sync. The excitement is carried very well, the Strings are consistently battering the Audience’s eardrums with incredibly high notes, and the Strings come in fast with the knife strokes allowing no rest by the Audience. As the attacker departs and Marion slowly slides down the wall and into the bath in her dying moments, heavy Cello and Double Bass movements seem to drag her body down. The serene sound of a Shower opens and closes the Scene. This makes the Audience uneasy. It makes the Audience realise that all of this action is taking place in the most normal of places, the Bathroom. The drain gurgles at the end of the Scene; Marion’s life is effectively â€Å"going down the drain†. This is one factor of how the Excitement of the Shower Scene is created as much by Technique as by Action or Dialogue. Another Technique used to create Excitement in the Shower Scene is the way the Scene itself was Edited. The Scene is very, very fast-paced. Action is rife and the editing of the Scene carries this. The Shots quickly snap between the knife, Marion and her attacker, Mrs. Bates. This is very skilful editing as over 75 shots are used in the Scene, all skilfully snapping into the next. The fast snapping of the Shots helps the Actors in their quest to convey extreme violence on-screen. The Shots themselves seem to be frenzied, bloodthirsty in their constant snapping. The Audience is bombarded by various different images, this makes them very confused. This is what Hitchcock envisaged. The Audience cannot focus clearly on anything in the screen as nothing appears long enough to become an ‘anchor’ of sorts. The Audience are left confused, afraid of what’s actually happening. Even when the attacker departs, we do not focus on Marion long enough to take in the damage she has most certainly suffered at the hands of Mrs. Bates. The shots continually snap to various objects of interest around the room, eventually panning slowly around and into her room. The money is very clearly focused on at the very end of the Scene. We know that the money has not been touched; this throws the Audience even more. They are now deeply afraid as this was, clearly, not a murder to get the money. The Audience are left to try and figure the motive out on their own. This Scene lasts for around 45 seconds, but contains over 75 Shots. This is very skilful editing. This clever editing is another way Alfred Hitchcock conveys the Excitement in the Shower Scene as much by Technique as by Action or Dialogue. A very peculiar aspect of this Scene is the Setting. Hitchcock cleverly used the seemingly ordinary bathroom as the place of the brutal murder of the Audience’s ‘anchor’ to the plot of Psycho. Before Psycho was released, no Film Audience had seen a Bathroom, in full, in a Film. Psycho changed all that. Hitchcock used the ordinaries of the Bathroom to cause massive unease in his Audience. To the people of the 1960’s, a Bathroom was a Sanctuary. It was a place you could go to be your most vulnerable, a very private space. While in the Bathroom you are very vulnerable, but most people do not think of that when inside. When showering, you are naked. You are as vulnerable as the day you were born, no clothing to hide or protect you from the outside world. You are defenceless whilst showering and to a 1960’s Audience, to show a Bathroom on screen would be the height of disgust. For Alfred Hitchcock to use a Bathroom as the sight of a brutal murder was completely unexpected. Never before had a toilet been shown in a film, never mind a woman being murdered in her Shower. This caused huge controversy in the Public, just as Hitchcock had intended. People were left unsettled to see a woman at her most vulnerable being killed. This was the biggest intrusion on someone’s personal and private spaces ever shown in front of an Audience. This use of Setting to unsettle greatly enhanced the excitement in the Shower Scene by creating fear. This is another method used by Hitchcock to create Excitement in the Shower Scene as much by Technique as by Action or Dialogue. The Shower Scene in Alfred Hitchcock’s Psycho is important to the film as a whole due to the main protagonist, Marion being murdered. This leaves the Audience without an ‘anchor’ in the Plot and we’re forced to search for another to see where the story will lead us next. We’re later introduced to Norman Bates’ point of view in the story and he replaces Marion as our ‘anchor’ in Psycho. However, the Audience remains suspicious of Norman so he does not take on the role of protagonist like Marion. In this essay I have explored the Shower Scene in detail and shown how Alfred Hitchcock created the excitement present in the Scene as much by Techniques, such as Editing and Music, as by Action and Dialogue. I have also, in my opinion, shown how important the Scene is to the film as a whole.

SWOT Analysis and Earth Care Program of Kimpton Hotels Free Essay Example, 2250 words

The Kimpton Group ensures that each of their locations is unique combining elegance with the whimsical. They design their hotels with the help of top quality designers and architects. They usually purchase existing property and modify it according to their needs rather than build an entirely new building. Flavor: Imaginative and fun restaurants and lounges, which feature highly capable chefs that are favored by both locals and travelers. Fun: Fun and enjoyment is a favored theme and necessary activities are made available to see that customers enjoy themselves. All efforts are made to see that the guests enjoy a friendly and welcoming atmosphere SWOT analysis of Kimpton Hotels: SWOT analysis of an organization will give a correct picture of its health. SWOT analysis is an acronym of strength, weakness, opportunities, and threats and is essentially an exercise to identify each of these elements for the organization. The company can use the SWOT analysis to provide recommendations on its development and progress. Through the analysis of these factors, they can understand which areas they are weak in and put in efforts to correct them. We will write a custom essay sample on SWOT Analysis and Earth Care Program of Kimpton Hotels or any topic specifically for you Only $17.96 $11.86/page