Physics, Chemistry and Biology: Post your doubts here!

Lost_Life

Lost_Life

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beewhiz997 said:
transistors have 3 parts, a base , collector, and emmiter... tell me what you want to know bcoz then i can explain
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um... i don't know where the voltages are collected at ( i just know that it should be greater than 0.666v)
and what happens is a resistor is put in the collector??:whistle:
AMEEN W INSHALLAH EVERYONE GETS A*
 
AAnsarii

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sara16 said:
I am having a big problem in http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Physics (0625)/0625_s10_qp_32.pdf with question 5, 9 and 10 please help me out! :(
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q5--
(a)paper falls with constant speed, Y? coz there's air resistance 4m below/friction....k? this equals to the weight(force) of the paper, n thus upward force=downward 4rce. n speed is constant coz of no acceleration.
coin falls with increasing speed: {opp of ppr} same air resistance, but d weight of the coin is larger, thus downward 4rce is larger than upward. thus the resulting acceleration (increasing speed).
(b) with vacuum there's no air resistance. so d ppr falls wid increasing spd ie acceleration.

q9--
(a) P is a diode, u need 2 learn dat, n it prevents d backflow of current
(b)
(i) pt A: current ALWAYS chooses the path of least resistance, so we'll ignore d 22ohms, n d resistance is thus 2 ohms.
(ii)pt B: u can c dat there are resistors in parallel, so u add up dose in series (22+2)ohms n in d nxt there's 8 ohms
Resistance in a parallel circuit=(resistance1*resistance2)/(resistance1+resistance2)
= 24*8/(24+8) =6 ohms
(c) {v look at conventional current, which flows 4m positive to -ve} thus, no current as diode is wrong way round. (look at d arrow in d diode, it shows how it'll allow d current)
(d)there's no chance of 2W in position C, so v rule dat out.
at A:- I=V/R = 4/2 =2A. P=VI =4*2 =8W, which is not d 1 needed
at B:- I=V/R = 4/8 =0.5A. P=VI =4*0.5 =2W!!! yuhoo! dat's it!
k?

q10--
(a)[dis is what i think] only frequency is being multiplied by 1.5, none of d settings r changed. u can c dat dere r 2 waves in d diagram, so d ans will b 2*1.5, which is = 3 k? there r 12 lines, vertically n horizontally, so 1 wave will occupy 4 vertical lines, an upper half will cover 2 lines n so will a lower half.
(b) i didn't understand dis part, will inshaAllah get back 2 u if i remember.

Hope u understood;)
All d best:)
Please pray 4 me 2.
 
Soban

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HEY Guys!
Im just too new to this forum thing but i wanted to know how do we study for paper 1 of physics ?
because we cant just solve past papers or memorize them so if any one can help me to know tht which part of syllabus is for p1 and how do i go through it >?;):)​
​
 
Lost_Life

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Transformers can only work with an ac supply so they can be stepped up ( higher voltage)
stepped down (lower voltage)
for a transformer to be stepped up it should have more coils on the second (OUTPUT, Secondary) than the first coil (PRIMARY,INPUT)
for a transformer to be stepped down it should be vice versa
At times a question will ask of you the number of coils given a number on the secondary or primary OR find the voltages of one of each
in that case use TURNS RATIO which is V(1)/V(2)=N(1)/N(2) THIS IS USED ONLY IF IT IS 100% EFFICIENT OR 99% EFFICIENT
we use low currents in transformers to minimize energy lose hence prevention of eddy currents
HOPE THAT HELPED!;)
 
beewhiz997

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we will do it said:
Can anyone pls explain me about transformers i need the exact explaination
Click to expand...
transformers are of 2 types, step up, and step down. a step up transformer increases the output voltage and a step down transformer decreases the output voltage.there is the primary coil (input) and the secondary coil(output). The official explanation of how transformers work: When AC is supplied to the primary coil it induces a rapidly changing magnetic field which travels through the soft iron core and cuts the secondary coil, inducing EMF. The amount of EMF depends on a number of factors, like turns of the coil and amount of current supplied. Hope i helped!:)
 
sara16

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AAnsarii said:
q5--
(a)paper falls with constant speed, Y? coz there's air resistance 4m below/friction....k? this equals to the weight(force) of the paper, n thus upward force=downward 4rce. n speed is constant coz of no acceleration.
coin falls with increasing speed: {opp of ppr} same air resistance, but d weight of the coin is larger, thus downward 4rce is larger than upward. thus the resulting acceleration (increasing speed).
(b) with vacuum there's no air resistance. so d ppr falls wid increasing spd ie acceleration.

q9--
(a) P is a diode, u need 2 learn dat, n it prevents d backflow of current
(b)
(i) pt A: current ALWAYS chooses the path of least resistance, so we'll ignore d 22ohms, n d resistance is thus 2 ohms.
(ii)pt B: u can c dat there are resistors in parallel, so u add up dose in series (22+2)ohms n in d nxt there's 8 ohms
Resistance in a parallel circuit=(resistance1*resistance2)/(resistance1+resistance2)
= 24*8/(24+8) =6 ohms
(c) {v look at conventional current, which flows 4m positive to -ve} thus, no current as diode is wrong way round. (look at d arrow in d diode, it shows how it'll allow d current)
(d)there's no chance of 2W in position C, so v rule dat out.
at A:- I=V/R = 4/2 =2A. P=VI =4*2 =8W, which is not d 1 needed
at B:- I=V/R = 4/8 =0.5A. P=VI =4*0.5 =2W!!! yuhoo! dat's it!
k?

q10--
(a)[dis is what i think] only frequency is being multiplied by 1.5, none of d settings r changed. u can c dat dere r 2 waves in d diagram, so d ans will b 2*1.5, which is = 3 k? there r 12 lines, vertically n horizontally, so 1 wave will occupy 4 vertical lines, an upper half will cover 2 lines n so will a lower half.
(b) i didn't understand dis part, will inshaAllah get back 2 u if i remember.

Hope u understood;)
All d best:)
Please pray 4 me 2.
Click to expand...
thank you so much ! inshAllah you will achieve great! you share you knowledge with others! ( highly appreciated)! :) pleae pray for me too..coz physics is the only hope for me to achieve great!
 
A

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tania said:
I am having problem with moments. Especially stable,neutral and unstable equilibrium..plx help!!!!!!!!!!
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an object is more stable when it's centre of gravity is lower
an object is stable when a vertical line passing through the centre of gravity falls within the base of support

a moment is a turning effect
it's the force into the perpendicular distance
look at this, it's good:
http://www.passmyexams.co.uk/GCSE/physics/turning-effect-forces.html#1

i'm not sure if that helps you but oh well :p
 
AAnsarii

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sara16 said:
thank you so much ! inshAllah you will achieve great! you share you knowledge with others! ( highly appreciated)! :) pleae pray for me too..coz physics is the only hope for me to achieve great!
Click to expand...
Salamun Alaikum
Jazakillah, i will inshaAllah pray 4 u, u 2 pray 4 me:). n also plz pray dat whatever limited knowledge Allah has bestowed us wid is used in d correct way, in His Way. Aameen. Jazakillah again
You'll inshaAllah do good, just do ur best and leave to Allah d rest. That's d mettle of d Muslim.

n about 10 b-- peak2peak dist is 6cm, Volts/cm is 5V/cm


when v multiply 2 get d voltage, ie 6cm*5V/cm, v get 30V
what i get is dat this value must be left unchanged, so in order 2 reduce d cm value, v must increase d V/cm value. They've asked us 2 half d dist, so v must double d V/cm, which will give us 10V/cm.:cool:!! n changing d time base will do u no good, so let's just leave it. [look at d marks too, its only 4 one mrk, so it's most likely dat it'll b sm] n dat's what d ms says.
Hope u got it
All d best, sis(y)

Salamun Alaikum wa rahmatullah
 
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