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Author Topic: ALL PHYSICS DOUBTS - POST HERE !!  (Read 225298 times)

Offline Ghost Of Highbury

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Re: ALL PHYSICS DOUBTS - POST HERE !!
« Reply #2175 on: May 26, 2010, 08:19:27 pm »
Quote from: Ivo on May 26, 2010, 08:14:26 pm
Sorry, here it is: http://www.freeexampapers.us/IGCSE/Physics/CIE/2009%20Nov/0625_w09_qp_31.pdf

I don't understand how it is worked out.

10ai) Step up transformer obviously.

    aii) Less current, less electrical energy lost, less heat energy given out

    b) P = V*I, I = 55k/22k = 2.5

    c) Rate of loss formula, P = I^2R = 2.5^2*3  = 18.75

    d) The overall voltage reduced from 22K Volts due to the resistance of the wire, till it reaches the receiving end.

I know this is confusing sh*t, it had appeared in my paper! nov 09! V = 2.5*3 = 7.5

from wiki "For example, an electric space heater may very well have a resistance of ten ohms, and the wires which supply it may have a resistance of 0.2 ohms, about 2% of the total circuit resistance. This means that 2% of the supplied voltage is actually being lost by the wire itself."

       e) 22000 - 7.5 -7.5 = 21985 (2 times 7.5 because there are two wires, each voltage dorp = 7.5)
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Offline Naruto123

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Re: ALL PHYSICS DOUBTS - POST HERE !!
« Reply #2176 on: May 26, 2010, 08:20:34 pm »
GUYZ do we have to change da temperature to kelvin or not ??? thx
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Offline Vin

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Re: ALL PHYSICS DOUBTS - POST HERE !!
« Reply #2177 on: May 26, 2010, 08:22:38 pm »
Quote from: 33oomar on May 26, 2010, 08:15:48 pm
guys i need help in q8 May / JUne 2007 Paper 3 Part B
PLEASE

b) i)

P =I V
I = P/V

=36/1

=3A

ii) V = IR

R = V/I

=12/3

= 4 ohm

iii) 1/R = 1/R1 + 1/R

1/R = 1/4 + 1/4

1/R = 2/4 = 1/2

so, R = inverse of 1/2 = 2 ohm


iv) E = P t

= 36 * 30

=1080 J

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Offline Malak

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Re: ALL PHYSICS DOUBTS - POST HERE !!
« Reply #2178 on: May 26, 2010, 08:23:06 pm »
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Offline Adzel

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Re: ALL PHYSICS DOUBTS - POST HERE !!
« Reply #2179 on: May 26, 2010, 08:23:21 pm »
Quote from: 33oomar on May 26, 2010, 08:15:48 pm
guys i need help in q8 May / JUne 2007 Paper 3 Part B
PLEASE
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Offline mdwael

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Re: ALL PHYSICS DOUBTS - POST HERE !!
« Reply #2180 on: May 26, 2010, 08:23:31 pm »
Thanks a lot VIN your the best!!! :) :D
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Offline Vin

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Re: ALL PHYSICS DOUBTS - POST HERE !!
« Reply #2181 on: May 26, 2010, 08:23:43 pm »
Quote from: 123456789 on May 26, 2010, 08:20:34 pm
GUYZ do we have to change da temperature to kelvin or not ??? thx

yes while using the formula ..

p1V1      p2V2
------ = -----
T1           T2
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Offline Adzel

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Re: ALL PHYSICS DOUBTS - POST HERE !!
« Reply #2182 on: May 26, 2010, 08:26:22 pm »
Quote from: ~VIN1094~ on May 26, 2010, 08:23:43 pm
yes while using the formula ..

p1V1      p2V2
------ = -----
T1           T2

only this one???
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Offline Weaam

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Re: ALL PHYSICS DOUBTS - POST HERE !!
« Reply #2183 on: May 26, 2010, 08:26:35 pm »
Can anyone please please tell me the answer and draw the diagram of Q4 b in o/n 08 second varient?
Please and thank you!
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Offline 33oomar

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Re: ALL PHYSICS DOUBTS - POST HERE !!
« Reply #2184 on: May 26, 2010, 08:27:06 pm »
Quote from: ~VIN1094~ on May 26, 2010, 08:22:38 pm
b) i)

P =I V
I = P/V

=36/1

=3A

ii) V = IR

R = V/I

=12/3

= 4 ohm

iii) 1/R = 1/R1 + 1/R

1/R = 1/4 + 1/4

1/R = 2/4 = 1/2

so, R = inverse of 1/2 = 2 ohm


iv) E = P t

= 36 * 30

=1080 J


Oh thanks a lot dude ......... r u takin' paper 3 tomorrow
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Offline Ashe

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Re: ALL PHYSICS DOUBTS - POST HERE !!
« Reply #2185 on: May 26, 2010, 08:27:40 pm »
I don't really understand why we use a relay in circuits. When they ask why a relay is used in a circuit? what's the full answer to that?

And another question, i saw this in a past paper but couldnt find it again =S
When someone is driving in a car, and the car suddenly crashes. What's the energy change of the driver?
I know its from kinetic, but into what?

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Offline eastrimx

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Re: ALL PHYSICS DOUBTS - POST HERE !!
« Reply #2186 on: May 26, 2010, 08:27:56 pm »
can someone help me with the question 4 in october/nov 2008 paper 3 first variant?

http://www.freeexampapers.us/IGCSE/Physics/CIE/2008%20Nov/0625_w08_ms_3.pdf
« Last Edit: May 26, 2010, 08:34:32 pm by eastrimx »
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Offline dodi23

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Re: ALL PHYSICS DOUBTS - POST HERE !!
« Reply #2187 on: May 26, 2010, 08:29:12 pm »
Quote from: Ashe on May 26, 2010, 08:27:40 pm
I don't really understand why we use a relay in circuits. When they ask why a relay is used in a circuit? what's the full answer to that?

And another question, i saw this in a past paper but couldnt find it again =S
When someone is driving in a car, and the car suddenly crashes. What's the energy change of the driver?
I know its from kinetic, but into what?



into sound, heat nd potential energy :P
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Offline Adzel

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Re: ALL PHYSICS DOUBTS - POST HERE !!
« Reply #2188 on: May 26, 2010, 08:29:43 pm »
Quote from: weaam on May 26, 2010, 08:26:35 pm
Can anyone please please tell me the answer and draw the diagram of Q4 b in o/n 08 second varient?
Please and thank you!

Rondom Jerky Motion
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Offline Ghost Of Highbury

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Re: ALL PHYSICS DOUBTS - POST HERE !!
« Reply #2189 on: May 26, 2010, 08:30:38 pm »
GUYZ , WHEN YOU ASK DOUBTS, PLEASE PROVIDE THE LINK TO THE PAPER, IT IS MUCH EASIER FOR THE PERSON TO ANSWER. PLEASE!

THANK YOU :D

@master math - Variant one says its micrometer.
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