Wednesday 15 May 2013

Two conducting wires of the same material and of equal lengths and equal diameters are first connected in series



Question 4:
Two conducting wires of the same material and of equal lengths and equal diameters are first connected in series and then parallel in a circuit across the same potential difference. The ratio of heat produced in series and parallel combinations would be –
Solution:
(c) Heat produced in the circuit is inversely proportional to the resistance R.

Let RS be the equivalent resistances of the wires if connected in series and RP  be the equivalent resistances of the wires if connected in parallel
Then RS =R+R=2R
And 1/ RP = 1/R +1/R
       1/ RP = 2/R
Or        RP =R/2
Now the ratio of heat produced is given by 
 
      = 1/4
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30 comments:

  1. Aditya Meshram5 May 2014 at 08:06

    Thank you very much.

    ReplyDelete
  2. wibhu sharma18 July 2014 at 23:55

    This is wrong you cannot put formula of series in parallel combination because the potential drop will b v/2 in series so the method is wrong

    ReplyDelete
    Replies
    1. Unknown23 August 2017 at 06:15

      This comment has been removed by the author.

      Delete
    2. Unknown20 July 2018 at 18:32

      This formula can be applied in heat

      Delete
  3. Unknown1 June 2015 at 00:18

    I don't understand how witbhu has incorrected the answer

    ReplyDelete
  4. Unknown13 February 2016 at 08:41

    Shouldnt it be i²R(s)t/i²r(p)t
    =2r/(r/2)=2×2r/r=4:1?

    ReplyDelete
    Replies
    1. Unknown10 October 2017 at 10:16

      Nope becoz the current will be different so they won't get cancelled out

      Delete
    2. Unknown17 July 2018 at 11:00

      Same condition with me bro

      Delete
    3. Unknown23 December 2018 at 23:14

      The fault in your method is that the current won't be same as the potential diff. is same in both cases but the total resistance is different

      Delete
  5. Unknown13 February 2016 at 08:42

    Shouldnt it be i²R(s)t/i²r(p)t
    =2r/(r/2)=2×2r/r=4:1?

    ReplyDelete
  6. Unknown9 September 2016 at 23:39

    If in series then :
    H=i2RT
    and in parallel:
    H=V2/RT

    ReplyDelete
  7. Unknown15 May 2017 at 19:55


    Wrong. it is 4:1

    ReplyDelete
    Replies
    1. Ashwin26 July 2017 at 09:05

      Its Correct.

      Delete
    2. Ashwin26 July 2017 at 09:06

      not 100% sure

      Delete
    3. Unknown7 March 2018 at 00:04

      No...its 1:4 only in parallel combination voltage is constant but current is not therefore voltage gets cancelled

      Delete
  8. Unknown17 August 2017 at 07:42

    Coorect100%

    ReplyDelete
  9. Unknown2 September 2017 at 00:36

    So wrong only 10% satisfactory

    ReplyDelete
  10. Blaaa....26 December 2017 at 08:07

    Not fully sure its cirrect..i git the answer 4:1

    ReplyDelete
  11. NexoMods28 December 2017 at 23:18

    Yup, this solution is wrong...
    Hence proved.

    ReplyDelete
  12. Unknown6 January 2018 at 06:26

    Series is to parallel is equal to 1 is to 4

    ReplyDelete
  13. bhuvana13 March 2018 at 21:26

    Why can't we use I^2RT for proving it?

    ReplyDelete
  14. Unknown21 June 2018 at 20:21

    How can hear is inversely proportional to resistance??but by the joules law of heating we know that heat is directly proportional to the resistance

    ReplyDelete
  15. Unknown22 June 2018 at 23:07

    U are 100%right

    ReplyDelete
  16. Unknown22 June 2018 at 23:30

    Sorry I was wrong it is 4:1

    ReplyDelete
  17. MarsG19 July 2018 at 06:24

    This answer is wrong
    It should be 4:1 by Joule's law
    Heat is directly proportional to resistance
    The answers in NCERT textbook is incorrect

    ReplyDelete
  18. Unknown9 October 2018 at 08:07

    yaar guys agar galat hai to sahi answer comment karo from a2z

    ReplyDelete
  19. Raina22 June 2019 at 10:10

    The answer is 100% correct cuz my teacher too solved by this method. But, i have a question, if according to joules law Power is directly proportional to resistance then how in this method is it inversely proportional to resistance?
    Plzz answer I wanna clear this concept....

    ReplyDelete

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