help needed on phys paper O/N 2007

[1992]

can anyone explain me question 6 b) part i) and ii)
i dont understand the mark scheme dont know where they got the values.
thanks in advance

 

[PlanetMaster]

Paper 2 or paper 4?

 

[British Council]

@ paper 2 dude.... Can anyone please explain that y aren't the two WIRES connected in PARALLEL??? I did a similar mcq questions in which wires in CABLE were connected in parallel. Please do reply.

ur assistance is highly appreciated....

 

[beacon_of_light]

Here goes the answer...

potential difference across the copper wires = 230 - 225 = 5V (that is easily understood by the question as 225 is the max decrease in voltage across shower unit)
here take the whole cable not the two wires connected in series or parallel as they asked about the max resistance of the CABLE!!!

R = V/I = 5/46 = 0.11ohms.

now part (ii)

the two wires are not in parallel since current from the power supply doesn't divide b/w the two wires .....and that is quiet clear from the diagram. for calculating area of each wire either use half the cable resistance or twice the length, and twice the length since we r using combined resistance of the two wires.
R = $ L/A
....you get the answer...

 

[azfar kashif]

can anyone explain me question 6 b) part i) and ii)
i dont understand the mark scheme dont know where they got the values.
thanks in advance

yar, part b)i) is quite simple... Total voltage generated by the shower was 230V....if max potential diff across the shower is 225V, this means that the max p.d across the cables is 230-225 Volts!!!!! That's ur v... U already have I, i.e. 46...... so, R= V/I

for part b) ii) the wires are not in parallel! That is because there are 2 outlets on each side of the shower.......... If there had been 1 outlet on one of the sides, the current would have split, but since there are equal outlets on each side, current does not need to be divided, so consider it series!!!!!! therefore, we take the length of wire as 16*2!!! Then, simply use the formula: R= resistivity *l/A

Hope, u understood!!!!

 

[1992]

thanks guys. this question took me ages to understant, i think the question is not well explained :S

 

[beacon_of_light]

you mean the above question??? Which part are you facing problem in?

 

[Dr.Ramsamooj]

Does anybody know where I can get the june 2010 papers for chemistry, physics and biology? When will they be posted on xtremepapers?

 

[Axa saleem]

As the Admin said, 1 week after the results are published.