Physics, Chemistry and Biology: Post your doubts here!

Iridescent

Iridescent

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daisyy said:
http://papers.xtremepapers.com/CIE/Cambridge IGCSE/Physics (0625)/0625_w11_qp_11.pdf can anyone please help me with question # 31?? Thanks guys!
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The answer is C. This is because as K is moved towards X, the resistance across XK decreases, therefore, its share of the voltage also decreases which makes bulb L1 less bright. On the other hand, the resistance across KY increases and so its share of the voltage also increases. This makes bulb L2 more bright.

daisyy said:
http://papers.xtremepapers.com/CIE/Cambridge IGCSE/Physics (0625)/0625_w06_qp_1.pdf I need help in question # 18!
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The answer is C. This is because the heating element heats the liquid, making it less dense. The less dense liquid rises up and the denser liquid which is the colder one, sinks. You have to see at which place it is easier for the liquid to rise up. That place is C.
 
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daisyy

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Iridescent said:
The answer is C. This is because as K is moved towards X, the resistance across XK decreases, therefore, its share of the voltage also decreases which makes bulb L1 less bright. On the other hand, the resistance across KY increases and so its share of the voltage also increases. This makes bulb L2 more bright.


The answer is C. This is because the heating element heats the liquid, making it less dense. The less dense liquid rises up and the denser liquid which is the colder one, sinks. You have to see at which place it is easier for the liquid to rise up. That place is C.
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Ohh thanks A LOT!!! :D that really helped! I also need http://papers.xtremepapers.com/CIE/Cambridge IGCSE/Physics (0625)/0625_s12_qp_12.pdf question # 33! Thanks
 
Mairaxo

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fatima hussein said:
Can someone help me with http://papers.xtremepapers.com/CIE/Cambridge IGCSE/Physics (0625)/0625_s08_qp_1.pdf question 34 and 37.. in question 37, shouldn't the voltage stay the same because the voltmeter is connected to the 100Ω so the 90Ω doesnt affect it? Am i wrong?
Also,http://papers.xtremepapers.com/CIE/Cambridge IGCSE/Physics (0625)/0625_s07_qp_1.pdf question 39, i dont understand half-life can someone give me the rules for it? thanks!
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Q34- A. when wire cuts the magnetic field it induces a current. wire moves only one time so deflection is only once and then theres no more currunt so its 0 again.
Q37- resistance decreases for the other resistor so less voltage passes through it and instead more voltage can pass through the 100ohm resistor thats why voltage increases a little :)
Q39- its D. half life just means the mass becomes half. For example there is a 10g radioactive substance. It has a half life of 5 minutes. So after 5 minutes it will become 5g. after another 5 min it will be 2.5g. always divide by 2. in this question they said half life is 5 hours. mass is 0.48g. so 5hours before testing mass had to be 0.48*2=0.96g. then 10 hours erlier it had to be 0.96*2=1.92g. then 15 hours earlier 1.92*2=3.84 and finally 20 hours earlier it was 3.84*2=7.68 :)
 
Iridescent

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daisyy said:
Ohh thanks A LOT!!! :D that really helped! I also need http://papers.xtremepapers.com/CIE/Cambridge IGCSE/Physics (0625)/0625_s12_qp_12.pdf question # 33! Thanks
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The answer is C. This is because resistance is directly proportional to current when the current is constant. To get the answer, we have to take the ratio of both resistances, which is X:Y = 2:1. Therefore, the ratio of the voltages should also be X:Y = 2:1, which is 8V:4V. Thus, the voltage across Y is 8V.
 
Iridescent

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Mairaxo said:
yeah but thats if its separate. here the water pressure is equally distributed between X and Y. Its the same concept as floating and sinking chapter :D
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Oh, okay. The pressure at all points is the same.
Thanx for clearing the doubt :)
 
Iridescent

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daisyy said:
http://papers.xtremepapers.com/CIE/Cambridge IGCSE/Physics (0625)/0625_w12_qp_11.pdf guys can u please help me with question # 18 in this paper? Thanks a billion!
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The answer is A. This is because large thermal capacity means that more heat energy is needed to be taken in to bring about a small temperature increase. Therefore, when the energy taken in is more, the energy given out will also be more. And, the temperature increase should also be large so that a large amount of energy is given out to cool to room temperature.
 
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