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Heating Effect Of Current... 
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#1
Aug506, 08:31 AM

P: 46

INTRODUCTION:Here is a problem on "Heating Effect Of Current".I can't understand a part of it.
EXACT PROBLEM: "A battery of emf E and internal resistance r is supplying current to an external resistance R.(a)Show that the power dissipated in R will be maximum when R=r.(b)What is the maximum power?(c)What would happen if the battery is shorted?" WHAT MY BRAIN SUGGESTED:(a)The current in the circuit is i=E/(R+r).Power dissipated is P=(i^2)r.Now putting the value of i, we find that P will be maximum when denominator is minimum,i.e. (Rr)^2 is 0. So, R=r. (b)Putting r in place of R in the power equation, we get maximum power as (E^2)/4r. (c) ***ERROR***The word "shorted" is not yet registered in the PHYSICS part of my brain .BRAIN CANNOT SUGGEST ANYTHING.SORRY. CONFUSION:What does "battery is shorted" mean?And what would happen if the battery is shorted? CONCLUSION:Physics Forums say that it is necessary to show that one has tried a particular problem in order to be answered.But what can one do if he cannot understand the meaning of a term?(I don't know what exactly "shorted" is).How will i prove that i've really tried part (c)?Nevertheless, i've tried to show that i know the other things of "Heating Effect Of Current".If you still don't believe me i have nothing to say. But if you do help me, thank you in advance. 


#2
Aug506, 09:07 AM

P: 21

Hello, I think shorted implies a short circuit, and the heating effect of current is joule heatingJoule's Law.



#3
Aug506, 09:16 AM

Mentor
P: 41,304

"The battery is shorted" means that instead of connecting an external resistance across the battery terminals you connect a plain conducting wire across them. Assume the wire has zero resistance and thus creates the socalled "short circuit".



#4
Aug506, 09:19 AM

P: 46

Heating Effect Of Current...
so in this case, what would happen if the battery is shorted. plesae explain. it is the first time i'm coming across short circuit problems. thanks.



#6
Aug506, 09:43 AM

P: 46

thanks a lot.



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