Physics: Post your doubts here!

[Snow Angel]

Suchal Riaz My teacher had not teach me anytime to half. Do we have to half ? :'(

Suchal riaz is ur teacher??

 

[Thought blocker]

Suchal riaz is ur teacher??

no, I tagged him coz MY teacher in India have not teach me such thing

 

[usama321]

Suchal riaz is ur teacher??

The wires are in series with each other. Just think of them as lying end to end. Won't you take the length of the whole wire, and calculate the cross sectional area of the wire? That's why you don't halve it

 

[Thought blocker]

The wires are in series with each other. Just think of them as lying end to end. Won't you take the length of the whole wire, and calculate the cross sectional area of the wire? That's why you don't halve it

Other wise we would halve it, eh ?

 

[usama321]

Other wise we would halve it, eh ?

why would we halve it? what is your approach of thinking when you say we would halve it?

 

[Thought blocker]

why would we halve it? what is your approach of thinking when you say we would halve it?

Snow angel asked why we dont half it. So I never halfed the area! So I am doing right or wrong ? ?

 

[usama321]

Had they been parallel to each other, we would have taken the length of only one wire, and then added their resistances by the parallel addition method

 

[Thought blocker]

Had they been parallel to each other, we would have taken the length of only one wire, and then added their resistances by the parallel addition method

Ok

 

[Snow Angel]

The wires are in series with each other. Just think of them as lying end to end. Won't you take the length of the whole wire, and calculate the cross sectional area of the wire? That's why you don't halve it

ok thnx

 

[meerul264]

Can someone please explain me the concept behind this question?

Q6
http://papers.xtremepapers.com/CIE/...nd AS Level/Physics (9702)/9702_s10_qp_22.pdf

And when it asks for line of best fit, do you draw a curve or a straight line of best fit? (Silly question, I know)

Thanks

 

[Hassan Ali Abid]

Can anyone plzz explain me the following part :-

Q. Use Lenz's law to explain why the input p.d and output e.m.f are not in phase. [2]

 

[usama321]

Can someone please explain me the concept behind this question?

Q6
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_s10_qp_22.pdf

And when it asks for line of best fit, do you draw a curve or a straight line of best fit? (Silly question, I know)

Thanks

Here

CB also has resistance. So there is some voltage across it too. The rest of the voltage is then equally dissipated across the two parallel wires

 

[Thought blocker]

Can someone please explain me the concept behind this question?

Q6
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_s10_qp_22.pdf

And when it asks for line of best fit, do you draw a curve or a straight line of best fit? (Silly question, I know)

Thanks

Line of best fit means a st. line

 

[Fahm Deen]

Oct/Nov 2010 /21 6.b . Please give me the solution with complete explanation. URGENT

 

[biscuitbiscuit]

Oct/Nov 2010 /21 6.b . Please give me the solution with complete explanation. URGENT

Okay, this is how i did this :
Power=V^2/R, therefore resistance of a heater is, R= V^2/P
R= 230^2/1000= 52.9 ohms

(i) Since the heaters are in parallel therefore voltage across them would be 230V
Total resistance of the circuit= 52.9/2= 26.45 Ohms
therefore power diss...= 230^2/26.45= 2000W= 2KW

(ii) Series combination, voltage across the heaters would be 115V
Total resistance of the circuit= 52.9*2= 105.8
therefore power diss...= 230^2/105.8= 500W= 0.5KW

(iii) bottom are parallel to each other, therefore their effective resistance= 26.45ohms
therefore the total resistance of the circuit= 26.45+52.9= 79.35 ohms

power diss..= 230^2/79.35= 666.6666...= 0.67KW

Hope it helps

 

[biscuitbiscuit]

http://papers.xtremepapers.com/CIE/...nd AS Level/Physics (9702)/9702_w10_qp_23.pdf
"Q8(b)" someone please

 

[Suchal Riaz]

I didn't get this thing, did u mean 1.5 to 3.5 ohms if not how did you get volts?

from graph

 

[biscuitbiscuit]

from graph

well the on the graph y-axis is labelled in ohms!

 

[Suchal Riaz]

Suchal Riaz My teacher had not teach me anytime to half. Do we have to half ? :'(

idk what you are talking about. i guess it's error?
powers multiply:
V=r²
so dV/V = 2dr/R
dR/R means fractional error in R(convention). like in R= 3 +- 0.1 R=3 and dR=0.1 so fractional error is 0.1/3=dR/R
when multiplying or dividing the fractional error add and if the power multiply.
such as :
M=AZⁿ
dM/M = dA/A + n(dZ/Z)
and dM = M[ dA/A + n(dZ/Z) ]

 

[Suchal Riaz]

well the on the graph y-axis is labelled in ohms!

oops.
i meant to say that the deflection will be small. if you work out the change in reading of volt meter as temperature is changed from 0 to 25 C it will be very small. if the change is small it means that the precision will be less.