Combined Science Double Award - 9204 OxfordAQA

Energy Resources

Aperçu

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. Every statement in this topic is set for both tiers, so nothing here is anybody else's problem.

Objectifs

  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.

Carte mentale

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Note de cours

A hospital on the edge of a town needs a standby supply that will start at three in the morning, on the day the mains 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 standby sets 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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Évaluation de la leçon

Félicitations, vous avez terminé la leçon sur Energy Resources. Maintenant que vous avez exploré le concepts et idées clés, il est temps de mettre vos connaissances à lépreuve. Cette section propose une variété de pratiques des questions conçues pour renforcer votre compréhension et vous aider à évaluer votre compréhension de la matière.

Vous rencontrerez un mélange de types de questions, y compris des questions à choix multiple, des questions à réponse courte et des questions de rédaction. Chaque question est soigneusement conçue pour évaluer différents aspects de vos connaissances et de vos compétences en pensée critique.

Utilisez cette section d'évaluation comme une occasion de renforcer votre compréhension du sujet et d'identifier les domaines où vous pourriez avoir besoin d'étudier davantage. Ne soyez pas découragé par les défis que vous rencontrez ; considérez-les plutôt comme des opportunités de croissance et d'amélioration.

  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 supply? 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 waste no energy D. Hydrogen cannot be burnt in an engine Answer: B
  5. A device is supplied with 600 J of energy and transfers 450 J usefully. What happens to the other 150 J? A. It is destroyed B. It is stored in a less useful way, warming the surroundings C. It is returned to the supply D. It becomes extra useful energy later Answer: B

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