G495 28th June 2016 - PRE RELEASE!Watch
Pre release came out last week for the A2 and AS course. We're the last year taking this syllabus so hopefully there will be enough people to start a chat.
Find A2 Pre release here
Practise questions curtoesy of Matthew Arnold school can be found here
I honestly hate this exam board. Eugh, the book that goes along with it is complete **** so i havent even used it this year. Instead I'm only going with the CGP revision book. Does anyone have a recommendation? I know there is the only revision website.
Thanks a lot for the questions and the link to the MAS website!
My teacher recommended the collins Physics book by dobson grace and lovett and i must admit it is very useful. It covers most of the topics and explains them in detail. it's a good reference book to have
1. 1Wh =60*60*1=3600J
2. 57 mins soapproximately 1 hour, use P=IV and equate E/t=IV and use constant current of35mA
3. total energy =22*3600*24*1 = 1900800E/m = 1900800/51= 37000J/kg (51kg for total mass, I checked on wikipedia, mass of 51kg is fortotal power supply i.e. all 3 batteries)
Catching the sun
1. A solar panelworks by allowing photons, or particles of light, to knock electrons free fromatoms, generating a flow of electricity. Solar panels actually comprise many,smaller units called photovoltaic cells. When light energystrikes the solar cell, electrons are knocked loose from the atoms in thesemiconductor material. If electrical conductors are attached to the positiveand negative sides, forming an electrical circuit, the electrons can becaptured in the form of an electric current -- that is, electricity. Thiselectricity can then be used to power a load, such as a light or a tool.
2. They consistof a thin layer of dielectric material, with a specially chosen thickness sothat interference effects in the coating cause the wave reflected from theanti-reflection coating top surface to be out of phase with the wave reflectedfrom the semiconductor surfaces. These out-of-phase reflected wavesdestructively interfere with one another, resulting in zero net reflectedenergy. In addition to anti-reflection coatings, interference effects are alsocommonly encountered when a thin layer of oil on water produces rainbow-likebands of color
.3. INVERSE SQUARELAW solar flux = 4*10^26/(150*10^11)^2 = 1.8*10^4 W/m^2 which is 1.8kW/m^2,real value is about 1.36kW/m^2 if you check on wikipedia.
4(a). Usefulpower = 0.2*5.6=1.12kW, solar flux = 18kW/m^2, use units to find answer toquestion.Area = 18/1.12 =16m^2 per array, real value is about 15m^2 per array on wikipedia.
4(b). Unit iswatts per kg of area which is P/M/A which is PA/M therefore, PA/m = 300. Totalarea is 30*16 = 480m^2 as there is about 30 panels facing the sun on the solarpanel. Then rearrange and m = 1.12*10^3*480/300 which is abput 120kg.
5. 120/11000 =1.1% so its not significant. Not sure about this or question 4b.
6. mv^2/r =GMm/r^2 and this goes to v^2=GM/r, sub v=2*pi*r/T and r^3= GM*T^2/4*pi^2,convert orbital time to seconds and r= 7013km
7. I HAVE NO IDEAhaha, i think they'll give you more information if the exam asks this
.8. Solar flux =4*10^26/(2.28*11)^2 which is 7.7kW/m^29. See method forother questions I CBA.
1.The plutoniumgradually decays
2. Efficiency =electrical power out/ thermal power in = 296/4394 = 6.7%
3.lambda =ln2/87.7 years = 7.9*10^-3 per year. Output after 11 years = 276^-lambda*t =271W In fact, theanticipated power output is less than this (210 W). As the plutonium cools, theRTG becomes even less efficient. 4.Ceramicmaterials are hard, stiff, strong and brittle. They have high melting pointsand arechemically unreactive. The fuel isthus more likelyto remain intact during a severe impact. If it comes into contact with othermaterials, e.g. water, it will not corrode.
5.RTGs could beuseful in deep-sea exploration; they could also provide power forlong-termapplications in remote places, e.g. for environmental monitoringinstruments in polar regions.
6. I will attach a picture.
7.A thermocoupleis an electrical device consisting of two different conductors formingelectrical junctions at differing temperatures. A thermocouple produces atemperature-dependent voltage as a result of the thermoelectric effect, andthis voltage can be interpreted to measure temperature. Thermocouples are awidely used type of temperature sensor. If the probe faces the sun, then oneside of the probe will be significantly warmer than the one not facing the sun.This great temperature difference increases the thermoelectric effect. On Earth,the temperature differences are not as great.https://as-a2-physics.wikispaces.com/file/view/Chapter+18.pdfhttps://as-a2-physics.wikispaces.com/file/view/Chapter+18+-+Worksheet+Answers.pdf
A new line of enquiry
1. v^2=GM/r sub M = mass of Earth and r=7000km, v=7600m/s
4. Magnetosphere isnt completely unofrm so magnetics field strength varies.
orbit isnt exactly spherical so radius will vary.
Answers for pre release from Matthew Arnold school
Hi all, I've made a youtube video on the advance notice article just going through a few things and looking at the topics that might come up. My own exams finish on the 2nd of June so I'll upload more videos after that with help on both exams and going through past papers!