Physics Module P1 Energy for the home

NJW330
Flashcards by NJW330, updated more than 1 year ago
NJW330
Created by NJW330 over 7 years ago
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Physics Flashcards on Physics Module P1 Energy for the home, created by NJW330 on 03/17/2014.

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Question Answer
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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