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Homework Help: Classical physics doubts

  1. Jan 10, 2008 #1
    1.is work done the dot product of force with displacement of the center of mass of the body or the point of application of the force??

    2.consider a battery whose terminals are connected by a pure conducting wire then since there can be no potential difference between any 2 points on a pure conductor...the net potential difference between any two points is zero...then how come there exists a potential difference between the two ends of the conductor??

    3.consider a terminal of a battery...if the battery is not connected to any external circuit..then does it mean that charge has accumulated on each terminal of the battery due to the constant driving force?? if so how do we know how much charge has accumulated on each end??

    4.we say that emf of a battery is the potential difference across its ends.... consider a battery of emf E.. does it mean that one terminal is at a potential of zero and that the other one is at a potential of E...or can it be that the terminals can have any potentials but they are such that their difference is always E?? does this differ from battery to battery??...

    5. once the circuit is complete and charges start flowing...will there be any net electric field near the terminals?? what about in the air near the conducting wires??

    6. i have read that the electric field inside the conductor is the potential difference divided by the length of the conductor....does it mean that if the length of the conductor increases then the electric field will be less?? what about in the above case when the resistance is zero??

    7.if you consider any small length of a conductor(with resistance) what causes the electric field between its two ends?? whatever charge goes in comes out so how come there is an electric field?? and how exactly is this electric field "transferred" from the ends of a battery to an point in a conductor?is this the main purpose of conducting wires??

    8. what will the electric field lines look like in an small length of the conductor??

    9.what causes a potential drop between the two ends of a resistor?? also what is the cause of heat in a resistor?? is it due to KE of the electrons being converted to thermal energy?? if that is the case then when electrons move in to the resistor let them have a velocity v.. let the resistor have a uniform cross section A....then since if they lose some of their KE their velocity must be reduced...but by conservation of charges the number of electrons going in must be equal to the number of electrons going out... this means that somehow the acceleration of the electrons due to the must act in such a way that the velocity remains constant throughout...how is this always the case??

    10. are work and heat the only two ways to transfer energy to or from a system??
  2. jcsd
  3. Jan 10, 2008 #2


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    Hi rohith291991 and welcome to the forums

    Your questions seem like homework questions. The https://www.physicsforums.com/showthread.php?t=94379" state that you need to show some work before you get help. What do you think are the answers to the questions and why?
    Last edited by a moderator: Apr 23, 2017
  4. Jan 16, 2008 #3
    these are NOT homework questions...their my own personal doubts... i dont see y they shud be in the homework thread nor do i understand y i received an infraction....obviously since ive come up with these questions...its obvious that im not able to answer them....this website doesnt seem to be helping me at all.... http://www.goiit.com is MUCH better....humph...
  5. Jan 16, 2008 #4
    neways ive cleared most of my doubts and here are my own answers to these questions...

    1.work done is the dot product of force with displacement of the point of application of the force

    2.the battery wud be shorted...

    3.absolutely yes...

    4.hmmm...well the 2 terminals recieve equal and opp charges...so i guess they must have equal and opp potential...(assuming same geometrical construction...)

    5.i guess there must be...but im finding it hard to grasp the concept of E field due to moving charges...

    6.im not sure...

    7.im not able to imagine... need sum help with this...

    8.i guess parallel

    9.potential drop is due to the potential applied by the battery...energy is lost due to collisions...and the velocity of the particles coming out NEED NOT be the same as the velocity with which they come in....BUT on AVERAGE this velocity is almost constant...

    10. i guess so...

    i really dont know what u guys want me to type...ive thought about these qs a lot and spent some sleepless nights...do u want me to type down all my thoughts??
  6. Jan 16, 2008 #5


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    It is so many questions.
  7. Oct 2, 2009 #6
    10. sound, light(electromagnetic waves and electricity, includes heat), potential energy, kinetic energy, gravitational, elastic,
    and all of these are in one way or the other related to the 4 fundamental interactions of the strong weak, electromagnetic and gravitational forces
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