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  1. S

    A2 Physics | Post your doubts here

    apparently he wants you to differentiate magnetic flux with respect to time. Emf = d (flux / time)
  2. S

    A2 Physics | Post your doubts here

    why is the rectification max voltage less than the ac input?
  3. S

    A2 Physics | Post your doubts here

    Whats holding the object in place is friction. So centripetal force has to be equal to friction. If it increases, friction wont be enough to hold the object in place. So as r increases, the centripetal force increases and friction cant hold it in place anymore.
  4. S

    A2 Physics | Post your doubts here

    You can just use the first formula mentioned in our syllabus, otherwise, press the reset button and forget everything I said to return to your original unconfused state :P Informations needs to go and come back... So I really dont support that concept much.
  5. S

    A2 Physics | Post your doubts here

    Bandwidth of fibre optic cables transmissions?? In coaxial wires, the braid act as a return wire for the signal. Where is the return pathway for the signal in fibre optic cables? Another cable?
  6. S

    A2 Physics | Post your doubts here

    Curious question:- Why did the microphones in the 1950s-1990s kinda make your voice changed. Like if you watch a really old video, they nearly have this same kinda of tone which is not their real true voice. Did they use different circuitry or signals were not well amplified or what?
  7. S

    A2 Physics | Post your doubts here

    First point, means it allow the mobile to call telephones. Last point, TDM involves sequencing groups of a few bits or bytes from each individual input stream, one after the other, and in such a way that they can be associated with the appropriate receiver. If done sufficiently quickly, the...
  8. S

    A2 Physics | Post your doubts here

    thts a not smart thing to say, course I will :) ;)
  9. S

    A2 Physics | Post your doubts here

    Please do not memorize formulas blindly. Understand that when a question asks for work done on gas then compression is positive. But when a question asks for work done by gas then compression is negative. So if you are asked to find the Increase in internal energy when there is compression, use...
  10. S

    A2 Physics | Post your doubts here

    We have to clear this solution cz its a main point in the syllabus. (b) Candidates should be able to recall that a carrier wave, amplitude modulated by a single audio frequency, is equivalent to the carrier wave frequency together with two sideband frequencies.
  11. S

    A2 Physics | Post your doubts here

    Never said anything was wrong...It depends on what formula you are using. Stick to the CIE formula and mentality :- INCREASE IN INTERNAL ENERGY = THERMAL ENERGY SUPPLIED TO SYSTEM +++++ WORK DONE ON THE SYSTEM. The other formula is mentioned in sources is :- INCREASE IN INTERNAL...
  12. S

    A2 Physics | Post your doubts here

    Correct ! Work done by gas is +ve with expansion! Work done by gas is +ve if you are using the formula Delta U = Thermal energy - Work done by gas But Work done by gas is -ve if you are using the formula U = Thermal energy + Work done on gas Get the difference? Pleasee, press the reset button! I...
  13. S

    A2 Physics | Post your doubts here

    1. oh ok , now i get it! thank you 2. uhmm, the bandwidth of an FM wave , like an AM , max sidebands x 2 right? Another question : I dont understand how there are frequency sidebands for AM. I thought only amplitude changes? But I meant for example, the bandwidth of an FM radio station is about...
  14. S

    A2 Physics | Post your doubts here

    1.according to the diagram, the anode is at a higher potential in the app booklet. 2.didnt quite get what you mean, example plz?
  15. S

    A2 Physics | Post your doubts here

    which year is this? if you have the answer, do we shade the two boxes at the right for satellite communiations because the cover from 10 cm to 1 mm. My advice to you, just memorize the frequencies. You can use 3x10^8 = Wavelength x frequency to find the wavelength.
  16. S

    A2 Physics | Post your doubts here

    I'm sorry you kinda lost me there. They wanna reduce the signal power to noise level. The signal power is the output power of the microphone after it is amplified. I used Pout= after amplification and Pin = before amplification.
  17. S

    A2 Physics | Post your doubts here

    I'm afraid the book has the "First Law of Thermodynamics" stated rather unclearly. It states that Thermal Energy = Internal Energy + Work Done BY system (gas) Rearrange to give Internal Energy = Thermal Energy - Work Done BY system. Nothing fancy here. They are assuming work done by system as...
  18. S

    A2 Physics | Post your doubts here

    Q1-How is the anode in an x-ray tube held at earth potential when electrons are accelerated through a voltage? Q2-How do we get the frequency of the transmission when we have the bandwidth provided? I know for AM waves, we divide bandwidth by 2. How about for FM and other means of communications?
  19. S

    A2 Physics | Post your doubts here

    b) 63 db = 10 log ( P out / P in ) c) attenuation dB = 10 log ( Pout / Pnoise ) length = attenuation / length x attenuation
  20. S

    A2 Physics | Post your doubts here

    There is a difference between work done on the gas and work done by the gas. Compression = work done on gas = +ve. Expansion = work done by gas = -work done on gas = -ve
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