IGCSE/GCSE/O & A Level/IB/University Student Forum

Qualification => Subject Doubts => GCE AS & A2 Level => Sciences => Topic started by: Asamy111 on June 07, 2010, 04:14:32 pm

Title: kirchhoff's laws
Post by: Asamy111 on June 07, 2010, 04:14:32 pm
hiii .. can any1 explain for me kirchhoff's laws .. the 1st and the 2nd .. cuz in the past pprs couldnt get how to solve them.. ???
Thanks for any help
Title: Re: kirchhoff's laws
Post by: CHEMMASTER6000 on June 07, 2010, 04:16:53 pm
if your doing cie then its not requred but basically , addition of hbr to alkene will privide a combining of the h and the br.

the H basically goes to the carbon with the most number of hyrdogen attached thats all
Title: Re: kirchhoff's laws
Post by: Asamy111 on June 07, 2010, 04:28:48 pm
Thanks for replyin "CHEMMASTER6000" .. wt ur saying i think its for chemistry. .. and m asking for physics
Thanks again i 4got to mention that its for physics
Title: Re: kirchhoff's laws
Post by: leebux101 on June 07, 2010, 04:53:27 pm
lol!!!  haha!! what is the world is the major/minor product law for chem doing in physics...
Title: Re: kirchhoff's laws
Post by: Twinkle Charms on June 07, 2010, 05:14:54 pm
kirchoff's 1st law.....
electrical charge is conserved....and it states that sum of current approaching a junction=sum of current leaving the junction.....see the diagram....I1+I2=I3+I4

kirchoff's 2nd law....also known as the loop rule
it states that total emf of the circuit=total potential difference across all the resistors in the circuit
Title: Re: kirchhoff's laws
Post by: dan.kl on June 07, 2010, 05:54:10 pm
CHEMMASTER6000 and Bakhtawar your gettin confused with Markovnikov's rule
...clearly not a chem master after all lol

K1 states that at any junction in a circuit, the current entering is equal to the current entering
its based on the conservation of charge - it says that current is conserved, so if current is conserved then charge must be conserved (as current = rate of flow of charge)

K2 states that around any loop in a circuit, the sum of the emf's = sum of pd's
its based on the conservation of energy - emf and pd are both forms of work done per unit charge, so if charge is conserved then energy must also be conserved
Title: Re: kirchhoff's laws
Post by: Darth Austrakast on June 07, 2010, 05:58:13 pm
lol @ chemmaster's response
@dan.kl :nycly explained thanx !
Title: Re: kirchhoff's laws
Post by: dan.kl on June 07, 2010, 05:59:56 pm
no problem :) its all good revision for my physics exam on wednesday haha
hope i helped
Title: Re: kirchhoff's laws
Post by: sabrina on June 07, 2010, 06:01:11 pm
kirchoff's 1st law.....
electrical charge is conserved....and it states that sum of current approaching a junction=sum of current leaving the junction.....see the diagram....I1+I2=I3+I4

kirchoff's 2nd law....also known as the loop rule
it states that total emf of the circuit=total potential difference across all the resistors in the circuit
absolutely correct. i wanna add that loop law is based upon conservation of energy
Title: Re: kirchhoff's laws
Post by: Asamy111 on June 07, 2010, 06:48:56 pm
Thanks all for helpin me .. bt my problem is solving the questions from the past pprs like the one m/j09 q 7 ..
Title: Re: kirchhoff's laws
Post by: leebux101 on June 08, 2010, 09:31:51 pm
lol...dude i am not confsuing chem with physics//...duh!

to do those kinda questions u shud loo at some sample questions first and try to get them...
Title: Re: kirchhoff's laws
Post by: [Spy] on June 09, 2010, 07:24:49 am
Thanks all for helpin me .. bt my problem is solving the questions from the past pprs like the one m/j09 q 7 ..

i] its obviously R because you have one series Resistor in the path.

ii] although its also only one resistor but its in PARALLEL, meaning the resistance is affected by the other parallel resistor. and here's something, when ever you have two resistors connected in parallel and they're identical. then total resistance is half of one of the resistors.

for example, if you have to 5 ohm resistors then (1/5 + 1/5)^-1=2.5 which is half 5, so the answer for this part is 0.5R

iii] you have two series resistors so thats 2R and then the total resistance of the parallel ones which is 0.5R calculated from before, so its 2.5R
Title: Re: kirchhoff's laws
Post by: CHEMMASTER6000 on June 09, 2010, 07:39:06 am
the law is in chemistry as well. didnt know it was part of physics.