Thursday, January 30, 2020

The efficiency of an eElectric motor Essay Example for Free

The efficiency of an eElectric motor Essay The efficiency of the motor in experiment 2 does decrease linearly with increasing mass as I predicted. Ideally the two graphs should follow each other since I used the same motor in each experiment. However from my graph you can see that my calculated efficiency for the second experiment is consistently about 9% higher than the calculated efficiency from my first experiment. This difference has probably been caused by the inaccuracy of the joule meter. This is inconsistent with my results from my calibration experiment. They showed that the joule meter always records more energy that it is receives and therefore if I correct my results for experiment 2 it would make the motor even more efficient. However the linear sections of the graphs have the same gradient and this shows that in both experiments the efficiency is varying in the same way. Extension: Aim: To measuring the efficiency of the electric motor as a generator and to establish if the system is time reversible. The experiment: See Diagram for circuit digarm. Experimental method: I will dropped a variety of weights a distance of 1. 12m and then I recorded the amount of electrical energy produced by the motor using the joule meter Acknowledged Errors 1. The inaccuracy of the joule meter-however I can use my calibration curve to correct for this 2. Friction in the pulley system 3. The weight has kinetic energy when I hits the ground and this energy is lost from the system thus reducing the efficiency of the generator. My Results: H=1. 12m load=10. 3 ohms Mass (kg) Average Time for full drop(s) Joules recorded Exp1x10 Joules recorded Exp2x10 Average number of joules recordedx10 %E. Energy Input (J) Graph: Explaining the graph: The energy I put in the generator is dissipated in three ways. 1. Useful energy is dissipated in the load 2. Energy is lost in the friction of the pulley system 3. When current flows through the internal resistance of the motor energy is lost 4. Energy is lost when the weight I drop hits the flaw It follows that because energy is conserved: The Potential energy of the weight= Power dissipated in load + Work done against friction +Energy Lost in the motors resistance +Energy lost as the weight hits the floor M=mass, I=current, F=friction force, R=resistance, V=final speed of weight In my analysis I have chosen to ignore the energy lost in the internal resistance of the motor. This is sensible since the energy lost in the internal resistance was insignificant compared to the energy lost in the load. To further simplify things I will also ignore the energy lost as the weight hits the ground. This factor was very small because my weights travelled quite slowly and they had small masses. Simplified formula for analysis: Efficiency If you assume that the work done against friction is constant this formula explains the 1-1/x form of my graph. For small weights the generator is inefficient since most of the weights potential energy is being used to overcome friction. For small the second term of the formula is large and the generator is therefore inefficient. This is shown by my graph. For large weights the work done against friction becomes insignificant and consequently the generator becomes more increasingly more efficient. For larger the second term would tend to zero and the efficiency should tend to 100%. My results do show that the efficiency increases for heavier weights however my results appear to approach an efficiency of 14% not 100%. This difference may be caused by the fact that for my larger weight the energy lost in the motors resistance and the energy lost as the weight hit the floor become significant. The inaccuracy of the joule meter may have also contributed to this difference. Is a the motor time reversible If my motor was time reversible it should behave in the same way irrespective of the direction of time. For example if you use electrical energy lift a weight with a motor if the system is time reversible you should be able to get the electrical energy back by dropping the weight. A motor is obviously time reversible to an extent since it can be used both as a motor and a generator. However my results show that for my experiment you are only able to retrieve a small fraction of the energy you used lifting when using the motor as a generator (about 2. 5 joules out of 150 or 2%). This inefficiency can be partially explained by considering the parts of the system that are not time reversible. This includes the friction in the system and the energy lost in the internal resistance of the motor. Here energy is lost as heat and sound that cannot be retrieved. Conclusion: In general my experiments went well and I was able to use my result to make some useful conclusions. I was very pleased with the accuracy of my results. If I had more time I would have taken more experimental reading so that I could get a more complete picture of what was happening. I would also have spent more time calibrating the joule meter since its inaccuracy had a large effect on my results. Bibliography: Sources used: 1) Nuffield Advanced Science Physics student guide 2 unit H to L, Published by Longman, ISBN=0-582-35416-1 2) Web page: Motors URL=www. srl. gatech. edu/education/ME3110/design-reports/RSVP/DR4/Motors. http 3) Encyclopaedia Britannica CD-ROM 4) Encarta 99 CD-ROM by Microsoft Show preview only The above preview is unformatted text This student written piece of work is one of many that can be found in our GCSE Electricity and Magnetism section.

Wednesday, January 22, 2020

Immigrant Workers in Phoenix :: Immigration Labor Immigrants Essays Papers

Immigrant Workers in Phoenix Before the sun even rises in Phoenix, out of the closing shadows of night, dark and quiet silhouettes begin to appear. They are the silhouettes of working men who rise before the sun rises, each with the hope of obtaining work and earning money to help support their families. These men are usually assumed to be immigrants without the proper paperwork to work in the United States. They are also better known as day laborers. These so-called â€Å"day laborers† congregate on street corners or in the parking lots of builders’ stores awaiting the arrival of employers who will hire them for a day’s work. Some cities have tried to ban this type of â€Å"recruiting† while others have accepted it as inevitable. In Phoenix alone there are an estimated 2,500 day laborers ready, willing and able to work each and every day that stand on street corners hoping and praying they will be picked up by someone to work. Some days their prayers are answered and on others they are not. Before September 11, 2001, you saw them everywhere – in hard hats on construction sites, working as landscapers, painters and just about anything else one can imagine. Today, these migrant workers are struggling under a sputtering economy and the harsh glare of the escalating U.S. homeland security system. To add even more problems to their already full plate, the immigration service in Phoenix is warning contractors against hiring undocumented day laborers. The warnings are taking a toll on many laborers in north Phoenix who had been getting constant work. â€Å"I’ve worked only two days since last week† said Ruben Fuentes, a native of Tijuana. At the break of dawn on a Tuesday morning, the 20-year-old Fuentes joined dozens of others at the corner of Greenway Road and 29th Street to wait for someone to pick them up. â€Å"It’s getting harder,† he added and from my viewpoint, it looked like more men were left standing than were picked up for work on the day I chose to visit. Unfortunately for everyone, contractors could face fines of up to $1,000 for each occurrence if they fail to fill out the proper immigration forms by the end of the workday said Victor Brower, deputy assistant district director for the Immigration and Naturalization Service in Phoenix.

Tuesday, January 14, 2020

Utilizing Online Social Networking Sites Paper

Utilizing Online Social Networking Sites Paper Class: BSHS/352 Technology is constantly expanding and making it easier and more convenient to communicate and network with individuals and various organizations that we may not otherwise of had the opportunity to connect with. One area of technology that is growing at a fast rate and offering individuals and businesses, rather it be their professional life or personal the opportunity to make lasting connections is social networking sites. Social networking has become an excellent tool for businesses and individuals to connect and share information that can prove vital to their business.Sites like Facebook and LinkedIn are becoming popular and are an effective way to grow your business whether it is through networking with similar organizations and getting beneficial information from them or expanding your cliental by reaching out to those who may need or want your services. LinkedIn has become a vital tool used by the working profession al, assisting them with making connections or linking up with other working professional to share what work and what doesn’t work as well as connecting them with local or online support groups or networking groups.Members of LinkedIn are able to create a profile that gives a detail list of their educational background as well as their work experience. Users are able to browse the social networking site to view the profiles of other individuals, organizations, or companies within their field and follow the organization of choice and their postings. My ultimate dream is to create a nonprofit organization that is geared toward targeting at risk youth and their families.The whole concept is to help the whole family and not just focus your attention on the youth that may be having emotional or behavioral issues but offer mental and emotional support for the entire family, implementing various programs and workshops that will assist the entire family in growing, working, and playin g together. Networking sites like LinkedIn can prove to be vital as I take the steps necessary to make this dream a reality. As I was browsing through the site I came across a few groups in my local area that met up monthly for lunch to discuss the ideas and challenges of those looking to start a nonprofit.I also took the time to search for companies or organizations that were geared toward working with and advocating for children. I was really quite excited to be able to look at their profile, view their web pages and doing so helped me to get some ideas and get my juices flowing. I have considered making connections with the various organizations I have seen on LinkedIn in hope that they could link me to information, people, and training opportunities that could possibly put me one step closer to my dream.I am also interested in going to the next luncheon for nonprofit communicators in Raleigh just to get feedback regarding my idea and you never know someone at one of these lunche ons could either help me get closer to making my dream a reality or can link me to an individual or organization who can. I have found sites such as LinkedIn can prove to be extremely beneficial in making lasting connections within the business community and it gives those with businesses the opportunity to link up with other businesses to get feedback, advice, and possibly connect you with someone who can help you take your organization or company to the next level.This site also enables professionals to come together with the common ground of helping and motivating each other. Within the human service field this site can connect you to so many resources that can only assist in providing your clients with the ultimate experience. Having a site where human service workers from all fields and from all areas can come together online and share their experience, advice, and resources can prove to be helpful to the community as a whole.LinkedIn not only connect likeminded people but it o ffers an opportunity to share information regarding training and workshops that could assist organizations in staying up to date with the latest software and/or regulations. Such training and workshops can keep your organization competitive and allows you to offer your clients the best possible service. The best way to keep any business or organization growing is to continue to gain knowledge in your particular field.Always be willing and open to learning and growing, this is what the training and workshops are there for to assist businesses and organizations in improving their techniques and staying relevant and competitive. Sites such as LinkedIn can offer you the ability to gain knowledge and training from some very successful people. Human service workers who use online social networking sites such as LinkedIn can find being affiliated with professional groups and connections to offer more than just sharing experiences, advice, training, and connections to resources.Another bene fit to being a part of an online community such as LinkedIn is the ability to request referrals from the connections you met online. Users can also request sponsorships or recommendations from other users. Human service workers who are affiliated with sites such as LinkedIn may also be able to connect with local churches that could assist connecting the human service worker to the communities that need their assistance the most. Employers often look at profiles on these online social networking sites to assist them in finding employees as well.Although social networking sites such as Facebook and LinkedIn are excellent tools to stay connected to various resources there are other technical tools that can be used to expand and maintain your connections. Smartphones have proven to be a vital tool to use as well with various applications directed at making the life of professionals easier. The goal of a human service worker is to effectively and efficiently assist the client in improvin g their lives and often times this requires connecting them to other resources.Social networking sites such as LinkedIn can assist human service workers in making numerous connections all at the touch of a mouse to various resources and training opportunities. Having online support that provide advice, training, and encouragement, of the human service worker can assist them in helping their clients meet their goals. Reference: 2012. LinkedIn. com. Retrieved from http//www. linkedin. com/home? trk_tab_home_top

Monday, January 6, 2020

We Googled You - Hbr Case Stydy - 5679 Words

www.hbrreprints.org HBR CASE STUDY AND COMMENTARY S hould Fred hire M imi d espite her on line history? Four commentators offer e xpert advice. We Googled You by Diane Coutu †¢ Reprint R0706A Hathaway Jones’s CEO has found a promising candidate to open the company’s flagship store in Shanghai. Should a revelation on the Internet disqualify her now? HBR CASE STUDY We Googled You COPYRIGHT  © 2007 HARVARD BUSINESS SCHOOL PUBLISHING CORPORATION. ALL RIGHTS RESERVED. by Diane Coutu The wind was howling and relentless as Fred Westen opened the door and called upstairs to tell his wife that he was home. While he waited for her to come down, he poured himself a shot of whiskey, tilting the decanter with†¦show more content†¦Bullish on a China Shop Fred left the house at 5:30 AM every day for his ofï ¬ ce at 1 Constitution Road. He had a lot of work to do, and there was not a moment to waste. Despite sales of $5 billion in 2006, Hathaway Jones had fallen on hard times. Four years ago, the privately owned U.S. retail chain had recruited Fred because of his imposing credentials and a lifetime’s experience of working with luxury brands and had charged him with waking up the company’s sleepy, conservative stores. It hadn’t been easy. Though aggressive outsourcing to suppliers in Mexico for some of the chain’s lower-tier brands had helped bring the company’s margins closer to industry standards, that was just a start. An avid consumer of his ï ¬ rm’s marketing research, Fred knew that the company’s image was getting old fast. Younger people across the United States, where Hathaway Jones had 144 shops and outlets, wanted more affordable clothing, with more ï ¬â€šair. The trend was starting to show up in declining numbers for the company’s highpriced—some said stodgy—designer clothes. Plans for radically revamping the company’s image and product line were in the ofï ¬ ng. Fred’s biggest bet, however, was to elbow in on China’s luxury goods market, which was growing by 70% a year. He had earmarked millions of dollars to open new stores in three of the largest cities, including Beijing and