IIT JEE , AIEEE Forum - Physics , Electricity

niki_07

hii !!!!!!
can u plz ans a very simple ques of mine ?
why is there a potential difference across a resistor?we say that pd is less than the emf b'cauz of internal resistance cumng back to the same point
i want to say why resistance leads to potential drop in a circuit ? wat is its role in p.d ?

phyana

i hope u wanaa physical interpretation.............

look............................

potential difference is the work done by a unit charge to move from one point to another.
consider a circuit wit a wire AB ,a battery C,and a resistor R.

THE POTENTIAL ALONG THE WIRE(excluding the resistance) is same.since no work has to done by a charge to mave in a conductor.because electric feild inside a conductor is zero or we can say tht the feild is perpendicular to the motion of the electrons.

now when it come to the resistance............the charge feels a resistance to its easy flow.........so some work has to be done by the charge to overcome this resistance.if we could get tht work (.........somehow........)and divide it with the total charge flowing u get the potential difference.............

from calculations we get tht the potential difference acrss the resistance is just the== i x R.

U CAN GET THE VALUE OF i from the ammeter put in the cicuit.

now ur second question..........

all cell have some thing inside them with which they work......
chemicals r common inside the batteries......these chemicals cant be expected to work wit 100% efficiency.the inefficiency in them effect the free flow of elctrons.
thus charges have to do some work to overcome the internal resitance wit in the cell.so the effective potential we get is the total potential(EMF) - potential lost due to resitance = effective potential of the cell....................

hope u got it................

if satisfied plz rate me................................

astatine19

potential difference is the difference in the electrical energy levels of two points. A resistor provides resistance to the flow of current through it. To overcome it, energy needs to be supplied. Thus, to go from one end of a resistor to another, u need energy; hence there is a difference in energy levels, creating a potential difference. A charge moving from one point to another will experience a change in its overall energy.
i know it sounds gibberish, bt this is the best i could frame it.

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