Physics - 9203 OxfordAQA

Energy Resources

Resumen

Somebody, somewhere, had to decide what would be burnt or turned or heated to light the room you are sitting in. That decision was not made by a physicist alone. It weighed how much a kilogram of the stuff carries, whether it can be kept safely in a tank behind a building, what it does to the air of the town, what it leaves behind when the plant is dismantled in forty years, and whether it will still be there for your grandchildren. Every one of those questions has a physics answer underneath a political argument, and this lesson is about the physics.

You will learn to read a fuel as a store with a price tag: so many megajoules in every kilogram, kept in a particular way, dangerous in a particular way. You will work out how much of a fuel a job actually needs once you allow for the share that goes into warming the neighbourhood instead of doing the job, and you will see why two stoves burning different fuels can need six times as much mass for the same hot pot. Then you will step up to the national scale: what separates a renewable source from one that runs out, why renewable and harmless are not the same word, and what wave, solar and geothermal schemes are genuinely good and genuinely bad at.

Objetivos

  1. Fuels are a useful store of energy; different fuels are suitable for different situations and are selected according to a range of factors, such as ease of storage, energy content and safety.
  2. When a fuel is used, some energy is transferred to the surroundings. Some fuels are more efficient than others.
  3. There is a range of energy sources used on a national and global scale. Their use has implications for society in terms of factors including renewability and the environmental impacts of extraction, use and disposal.
  4. A range of technologies have been developed to provide energy in a renewable way, such as wave power, solar power and geothermal power. Students should be aware of these and other examples and be able to identify advantages and drawbacks with their use.

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Nota de la lección

A hospital on the edge of a town needs a generator that will start at three in the morning, on the day the grid fails, and keep running for two days without anyone visiting it. Physics will tell you that hydrogen carries more than twice as much energy per kilogram as diesel does. Nobody builds hospital generators that run on hydrogen. The reason has nothing to do with the size of that number and everything to do with the other questions: what would the fuel have to be kept in, how big would the vessel be, and what happens if it leaks into a corridor.

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Evaluación de la lección

Felicitaciones por completar la lección del Energy Resources. Ahora que has explorado el conceptos e ideas clave, es hora de poner a prueba tus conocimientos. Esta sección ofrece una variedad de prácticas Preguntas diseñadas para reforzar su comprensión y ayudarle a evaluar su comprensión del material.

Te encontrarás con una variedad de tipos de preguntas, incluyendo preguntas de opción múltiple, preguntas de respuesta corta y preguntas de ensayo. Cada pregunta está cuidadosamente diseñada para evaluar diferentes aspectos de tu conocimiento y habilidades de pensamiento crítico.

Utiliza esta sección de evaluación como una oportunidad para reforzar tu comprensión del tema e identificar cualquier área en la que puedas necesitar un estudio adicional. No te desanimes por los desafíos que encuentres; en su lugar, míralos como oportunidades para el crecimiento y la mejora.

  1. Which of these is a renewable energy source? A. Coal B. Natural gas C. Geothermal D. Uranium Answer: C
  2. A fuel has an energy content of 40 MJ per kilogram. A burner using it is 30% efficient. How much useful energy is delivered by burning 2.0 kg of the fuel? A. 12 MJ B. 24 MJ C. 80 MJ D. 240 MJ Answer: B
  3. A hospital must have electricity all night. What is the main drawback of supplying it from solar panels alone? A. Solar panels release sulfur dioxide B. The output falls to zero at night, so storage or a second source is needed C. Solar panels can only be built where the rock below is hot D. Solar panels destroy the mudflats in an estuary Answer: B
  4. Hydrogen holds about 120 MJ per kilogram and diesel about 45 MJ per kilogram. Why is diesel still chosen for a standby generator? A. Burning diesel releases no carbon dioxide B. Diesel is a liquid at ordinary pressure, so far more energy fits into a plain tank C. Diesel engines are 100% efficient D. Hydrogen cannot be burnt in an engine Answer: B
  5. Which renewable source gives an output that can be predicted years in advance? A. Wind B. Solar C. Tidal D. Wave Answer: C

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