643570
| Frage | Antworten |
| What is specific heat capacity? | How much energy you can store |
| It takes 5000j to heat 50g of a substance by 40 degrees C . Calculate its specific heat capacity. | SHC=Energy/(Mass x temp change) =5000/(0.05 x40) =2500j/kg/C |
| Explain why heating a pan of boiling water doesn't increase its temperature? | Once its reached boiling point it can't get any hotter |
| How much energy is needed to boil a dry pan of 500g of water to 100c | Energy = mass x specific latent heat (slh) =5000/(0.5 x40) = 1130000j |
| Briefly describe how heat is transferred through a) conduction b) convection and c) radiation | Conduction= goes from hot to cold Convection= when particles move from the hotter region to the cooler region Radiation= heat transferred from the sun |
| Describe how heat radiation is used to cook food a)under a grill b) in a microwave | A grill cooks through infa red heat, a microwave uses radiated heat putting microwaves through the food |
| Describe three ways of saving energy in the home and how each one works | 1-loft insulation- this keeps warmth in by using fibre glass wool to reduce conduction 2-double glazing- keeps air in the middle of the windows and reduces conduction 3- Draught proofing -strips of foam and plastic around doors and windows stops hot air coming out. |
| How much energy is wasted in a hair dryer thats 20% efficient has a total energy input of 200 0000 j ? | Efficiency = useful energy energy output/total energy input, so useful =efficiency x total energy= 0.2 x 200 000=40,000. Wasted energy = total energy input - useful energy output= 200 000 - 40 000=160 000 |
| Briefly describe what happens to a wave when its a) diffracted b) refracted | when its diffracted the signal strength is better, refracted helps the radio waves travel further |
| seven types of electro magnetic waves | 1-radio waves 2-micro waves 3-infared 4- visible light 5-ultraviolet light 6-xrays 7-gamma rays |
| Why is morse a code a digital signal | Because it can last a longer amount of time |
| Explain how lasers are used in CD players ? | They use lasers to read digital information and to cut into billions of pits in the CD to get information |
| Explain how infa red radiation is used to control electrical equipment | It picks up hot objects, the hotter the objects the more infared radiation it gives out |
| Explain why long wave radio waves can bend around obstacles? | The long wave radio waves refract (bend)around the earth |
| What happens to radio waves in the iron sphere ? | The top of the wave speeds up but not the bottom as much |
| Give two disadvantages DAB ( Digital Audio Broadcasting) | 1- the sound quality is usually not as good as FM 2- There are a limited number of DAB transmitters so some areas have no signal at all |
| Describe how satellites are used for communication ? | Microwaves are used for satellite communication , that means it will pass easily through earths watery atmosphere with not too much absorbtion |
| Why are scientists concerned about the danger of mobile phone usage and the thinning of the ozone layer? | The microwaves can go into your body when using a mobile phone or if you live near a mobile phone mast, this can damage your health. Microwaves from mobile phones can also burn the ozone layer as it has moisture in it which attracts the microwaves |
| Explain the difference between analogue and digital? | Analogue signals can vary Digital signals are just on or off, there is no inbetween |
| Why are CFC's so bad ? | CFC's can hurt the ozone layer as the gasses react with it and the molecules break up, this lets UV rays through which are harmful to humans |
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