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Description
Flashcards by harry.vinall, updated more than 1 year ago
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Created by harry.vinall
over 10 years ago
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| Question | Answer |
| What is the difference between primary and secondary sources of energy? | Primary energy sources are those used in the form they are found e.g. nuclear fuels or wind whereas secondary sources are produced from primary energy sources e.g. electricity. |
| How has our choice of energy sources changed over time and what problems could this could? | In 1850 most of our energy came from wood but over time fossil fuels have become our main source of energy, with nuclear also becoming an important fuel more recently. This could be problematic as burning fossil fuels produces carbon dioxide, a greenhouse gas. Other environmental include damage from coal mining, oil spills and production of sulfur dioxide, which contributes to acid rain. |
| What is the equation for energy transferred? | Energy transferred= power x time. If power is measured in watts (W, energy is measured in joules (j) and time is measured in seconds. If power is measured in kilowatts (kW) energy is measured in kilojoules (kJ). If energy transferred is measured in kilowatt hours (kWh), time is measured in hours and power is measured in kilowatts (kW). |
| What is the equation for power? | Power is how quickly energy is transferred by a device and is calculated through the equation power (W)= voltage (V) x current (A). A higher voltage means more energy is transferred and a higher current means the energy flows faster. |
| A lightbulb changes 100J of electrical energy into 10J of light energy and 90J of heat energy, draw a Sankey diagram. | |
| Define energy efficiency | The ratio of total energy transferred that is useful, given by the equation: efficiency= energy usefully supplied/ total energy supplied |
| How do generators produce electricity? | The generator has two main parts: a stationary coil made up of hundreds of turns of wire (the stator) and a large rotating electromagnet (the rotor). This works through the principal that moving a magnet near a circuit caused an electric current to flow through it. The rotor is spun by a turbine which produces a voltage across the coil of wire. Primary fuels provide the energy needed to turn the turbine. |
| What are the main stages in producing electricity from fossil fuels? | fuel burnt in furnace; water heated to produce; steam turns a turbine; turbine spins a generator; electricity produced by generator. In a gas powered power station the gas itself is burned and spins a set of turbines whilst heating steam to carry out the process outlined above. |
| Outline how energy is produce in nuclear power stations. | The reactor contains nuclear fuel rods, which produce heat. Control rods are raised or lowered to control the amount of heat produced. Water circulating through pipes leaves react and is put under high pressure by the water pressure, this means it reaches high temperatures. A second set of pipes filled with water surrounds these heated pipes. Heat is transferred to water in the second set of pipes changing to steam. |
| What is the difference between irradiation and contamination? How does this link to nuclear power stations? | Something is irradiated if it is in the path of radioactive material, this doesn't mean it becomes radioactive. In contrast something is contaminated if radioactive gases, liquids or particles mix with it, making it radioactive. This links to nuclear power stations as they produce nuclear waste. Most of this waste is of low radioactivity, but some is highly radioactive. To prevent contamination this waste is converted into glass, or mixed with concrete contained in steel drums so it can't contaminate its surroundings. |
| Give two examples of renewable energy sources and for each identify the positives and negatives. | Using hydroelectric dams provide clean energy and are cheap to run once built. However they are costly to build and the dams must be maintained. In addition they flood large areas and vegetation on the side of the river dies and rots, releasing greenhouse gases. Wind turbines use wind to spin turbines directly. The negatives are that they are unreliable and have to shut down if it gets too windy. |
| Why must a balance by reached between voltage and current when supplying electricity? | Supplying electricity at a low current reduces energy loss in transmission, this means a very high voltage is needed for enough electricity to be supplied. This voltage has to be reduced when delivered to consumers for safety reasons. In the Uk energy is supplied at 230V because it is large enough to supply useful amounts of energy, despite this it can cause electric shocks. In other countries a lower voltage is used but this means overheating is more likely as a higher current is needed. |
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