Physics, Chemistry and Biology: Post your doubts here!

[ZaqZainab]

should be C...cause only it has both clockwise and anti clockwise moments ...in A..it is both anti clockwise!

got it thanks

 

[fatima hussein]

i have doubts.

In Physics 0625 Paper 1:

http://papers.xtremepapers.com/CIE/Cambridge IGCSE/Physics (0625)/0625_w11_qp_12.pdf

Question 11: Why is it C?

Question 15: I dont understand why it is not B?

Question 29: Why A?

In Another Year:

http://papers.xtremepapers.com/CIE/Cambridge IGCSE/Physics (0625)/0625_s11_qp_12.pdf

Question 1: Why Not B

Question 8:

Question 10

Question 17

Question 18

Question 23

Question 24

Question 27

Question 29

Question 31: why not C

Question 34: why not B?

Question 35: why not D

Finally Question 37: I dont understand it.

I'd really appreciate if someone answers my doubts Thanks

 

[fatima hussein]

Also In: http://papers.xtremepapers.com/CIE/Cambridge IGCSE/Physics (0625)/0625_w12_qp_12.pdf

Question 13: Why D?

Question 16: why not B?

Question 20: Why not A?

Question 21: why not B?

Question 28: Why not C?

Question 36: why not C?

In: http://papers.xtremepapers.com/CIE/Cambridge IGCSE/Physics (0625)/0625_s12_qp_12.pdf

Question 5: why not A?

Question 9

Question 18

Question 24: Why not B?

Question 31: why not C?

Question 33: why not D?

Question 34: I dont understand it.

Thanks Again.

 

[sourov97]

http://papers.xtremepapers.com/CIE/Cambridge IGCSE/Physics (0625)/0625_s11_qp_12.pdf
Q 11 - ans C because as the volume decreases Pressure increases...cant be B cause a pressure was initially measured! see the question
Q 15 - cant be B cause both the can is open...there must be temperature loose to the surroundings..should be A cause the insulated one looses heat slowly than the other
Q 29 - A because adding 'parallel' decreases the effective resistence or overall resistance (consider the formula to find resistance in parallel [ 1/Rp = (1/R1) + (1/R2)...]...adding in series increases the overall resistance [ Rs = R1 + R2 ....]....opt D is not correct because V is same across every components in series circuit!

 

[sourov97]

http://papers.xtremepapers.com/CIE/Cambridge IGCSE/Physics (0625)/0625_s11_qp_12.pdf

Q 1 - d = 330*0.4 = 132...but as the sound reflects back (echo) it covers 2 equal distances - one from bat to wall and the other from wall back to the person!..so divide the d by 2 to get the distance to wall.
Q 8 - 'some ice has melted'....the others still remains...also 'what is the temperature of the remaining ice' indicates that it should be A 0 C..ice cannot be present in 2 4 or 8 degree C
Q 10 - the best conductor of heat will conduct heat more efficiently and melt the more wax...hence less balls should be left!...ans opt A
Q 17 - work done = force * distance ...( niether the force nor the distance to lift the hays have changed)..so W = same but as P = W/T...so as the work done is same but time is less...hence power will increase!
Q 18 - ans should be B...all other methods use the speed of water(current)
Q 23 - should be D ....frequency doesnt change ever....in dispersion of light..the darker the colour the less they are refracted..refraction occurs because of the speed difference...
Q 24 - C as it is a fact...look out for the definition of wavefront
Q 27 - C or D...most probably C as i heard capacitors store energy...but it hence stores current as well..capacitors are used in time delay ...ex - light in weedings..goes on and off!
Q 29 - it is given that as temp increases R decreases..so R will decrease as well as V ( V proportional to R ...since I in series circuit is same everywhere!)
Q 31 - can be D...as I after flowing through Z can flow through Y and again through Z...but i am confused...as due to excess current the lamp should go off!
Q 34 - should be D...'step down transformer'....more turns in primary and less turns in secondary!
Q 35 - both circuit breakers and fuse have same function...so should be B
Q 37 - should be C...hl = initial amount * (1/2)^n.... where n =no. of half lives!
i am not sure about any of the ans!...i am from GCE o level...but still practising ur Qs as tomorrow i have physics...so r my ans correct!??

 

[Iridescent]

i have doubts.

In Physics 0625 Paper 1:

http://papers.xtremepapers.com/CIE/Cambridge IGCSE/Physics (0625)/0625_w11_qp_12.pdf

Question 11: Why is it C?

Question 15: I dont understand why it is not B?

Question 29: Why A?

In Another Year:

http://papers.xtremepapers.com/CIE/Cambridge IGCSE/Physics (0625)/0625_s11_qp_12.pdf

Question 1: Why Not B

Question 8:

Question 10

Question 17

Question 18

Question 23

Question 24

Question 27

Question 29

Question 31: why not C

Question 34: why not B?

Question 35: why not D

Finally Question 37: I dont understand it.

I'd really appreciate if someone answers my doubts Thanks

w11:
Q11: This is because pressure and volume are inversely proportional if temperature is kept constant. If the volume is decreased, the pressure will increase.

Q15: It is not be because in B because in B, they show that no heat is being lost from the insulated can. However, heat will be lost from the insulated can by evaporation and convection but it will be slower than the insulated can. Hence, the answer C.

Q29: It is A because when another resistor is connected in parallel, the combined resistance is less than the resistance of one of the resistor. As resistance decreases, the current will increase because they are inversely proportional when the voltage is constant. B and C will both decrease the current and D will have no effect.

S11:

Q1: It is not B because the sound is an echo. We have to take twice the distance (to the wall and coming back from the wall). So, the equation will be: speed=2*distance/time.


Q8: It is A because during melting the temperature of the ice remains unchanged. It begins to rise only when all the ice has melted.

Q10: The better the conductor, the further will the heat reach in the rod. So, the answer is A because most number of balls have fallen showing the heat has reached the farthest point.

Q17: The answer is D. Work done= force * distance. As the weight of the hay and the distance moved remains unchanged, the work done remains unchanged. As, power= energy/time, the power output will increase if the time taken to lift the boxes decreases.

Q18: The answer is B i.e., nuclear fission. The energy released by nuclear fission is used to boil water which is used to run the turbines.

Q23: The answer is D. When white light enters the prism, the speed of different lights decreases according to their respective refractive index. The speed of violet light decreases more therefore, it is more bent towards the normal.

Q24: The answer is C. Wave fronts are lines that represents waves. They can be either circular or straight. A and B are wrong because distance x is the wavelength. D is wrong because 3 waves are produced in 2 seconds while frequency is the number of complete waves produced in one second.

Q27: The answer is D.

Q29: The answer is A. When the temperature of the thermistor increases, the resistance of it decreases. As resistance and voltage are directly proportional at contant current, the voltage across the thermistor will also decrease.

Q31: The answer is not C because if we look carefully, the path of all the bulbs is complete. The switch does not control the current through any of the bulbs.

Q34: The answer is not B because if it is B, the output voltage will increase instead of the decreasing. For decreasing the output voltage, the number of turns in the primary coil have to be more than the number of turns in the secondary coil, with correct proportion according to the ratio of the voltages.

Q35: It is not D because a circuit-breaker also does the same work as a fuse. Both of them prevent too much current flowing in the wires.

Q37: The half-life of a radioactive isotope is the time taken for any sample of it to decay to half its original value. As the half-life is 5 days, the amount of the material left after 5 days is 400/2 = 200mg. after another 5 days, it will be 200/2 = 100mg. So after 10 days it is 100mg.

 

[ZaqZainab]

i have doubts.
In Physics 0625 Paper 1:
http://papers.xtremepapers.com/CIE/Cambridge IGCSE/Physics (0625)/0625_w11_qp_12.pdf
Question 11: Why is it C?
Question 15: I dont understand why it is not B?
Question 29: Why A?
In Another Year:
http://papers.xtremepapers.com/CIE/Cambridge IGCSE/Physics (0625)/0625_s11_qp_12.pdf
Question 1: Why Not B
Question 8,10, 17, 18, 23, 24, 27, 29
Question 31: why not C
Question 34: why not B?
Question 35: why not D
Finally Question 37: I dont understand it.
I'd really appreciate if someone answers my doubts Thanks

Okay so firstly i would ask yo not to write with that many spaces my dear!!
http://papers.xtremepapers.com/CIE/Cambridge IGCSE/Physics (0625)/0625_w11_qp_12.pdf
11 the less the volume the more the pressure so by time the volume increases , it increases in B and in C but they have said they measured the pressure in the starting which means 0 time the pressure is already what is in the cylinder
15- No it can't be B heat is Lost from the top
29-A as adding another resistor for Parallel the total resistance becomes low and when resistance decrease the current increases
http://papers.xtremepapers.com/CIE/Cambridge IGCSE/Physics (0625)/0625_s11_qp_12.pdf
1- they have mentioned ECHO so 132/2
8- ICE is always 0 degrees
10- best conductor will let more heat pass through them so the wax will become heated and fell down the one with the least should be the answer here A
17- work done is force*Distance the force is the same the mass is the same all the time and the distance is the same so no change and output power increase the wheel spins faster..
18- for nuclear fission. have you studied about it?? here is a link http://www.bbc.co.uk/schools/gcsebi...e_2011/energy/generatingelectricityrev7.shtml which might help
23-D should be the answer when light enters air to glass the speed decreases if it decreases more the more it will bent form the normal. so red is moving less away so the speed does not decrease that much as Violet
24- C must be the answer X is the Wave length and Y are 2 waves and D is not right because the frequency is the waves in 1 second
27- Dude A capacitor (originally known as condenser) is a passive two-terminal electrical component used to store energy in an electric field. It is time delaying it is there in a Camera Led
29- whenever Resistance decreases Voltage decreases with it
31- all the circuits are complete
34 for a step down transformer the primary has more number of turns than secondary
35 a circuit breaker can ALSO be used
37- 400mg half life is 10 days means after 5 days it will be half that is 200mg so after more 5day 100mg

Also In: http://papers.xtremepapers.com/CIE/Cambridge IGCSE/Physics (0625)/0625_w12_qp_12.pdf
Question 13: Why D?
Question 16: why not B?
Question 20: Why not A?
Question 21: why not B?
Question 28: Why not C?
Question 36: why not C?
In: http://papers.xtremepapers.com/CIE/Cambridge IGCSE/Physics (0625)/0625_s12_qp_12.pdf
Question 5: why not A?
Question 9
Question 18
Question 24: Why not B?
Question 31: why not C?
Question 33: why not D?
Question 34: I dont understand it.
Thanks Again.

http://papers.xtremepapers.com/CIE/Cambridge IGCSE/Physics (0625)/0625_w12_qp_12.pdfokay so now you have got so MANY doubts
13 i have gave you a link earlier
16- it is B -_-
20- it is A
21- because 5/20 is A which is 0.25Hz
28 is B we don't want the 4th switch
36 they have asked being PRODUCED
Sorry about the other paper but i don't really have time now you've got A lot of doubts i would suggest you to study again!

 

[Iridescent]

Q26.
Why is the answer C? According to me, it is supposed to be A.
Is it that with the bulbs connected in parallel, the resistance decreases. But when the bulb is removed, the resistance increases so the current decreases.

 

[ZaqZainab]

Q26.
Why is the answer C? According to me, it is supposed to be A.
Is it that with the bulbs connected in parallel, the resistance decreases. But when the bulb is removed, the resistance increases so the current decreases.

When it was in Parallel the resistance is LESS than being IN SERIES so the current is more in parallel would increase the resistance and decrease the current

 

[nononona]

do the kinetic energy increases as the car accelerates why????

 

[Iridescent]

When it was in Parallel the resistance is LESS than being IN SERIES so the current is more in parallel would increase the resistance and decrease the current

Yes, that is what I said above in different words. When one of the bulb is removed (that's what the question says), the resistance increases and the current decreases.

 

[ZaqZainab]

do the kinetic energy increases as the car accelerates why????

Yes it does.
Kinetic energy is energy of motion
And Acceleration is the INCREASE in the rate of speed
Speed increase, Motion increases

 

[nononona]

Yes it does.
Kinetic energy is energy of motion
And Acceleration is the INCREASE in the rate of speed
Speed increase, Motion increases

oh ok thanks

 

[ZaqZainab]

Yes, that is what I said above in different words. When one of the bulb is removed (that's what the question says), the resistance increases and the current decreases.

sorry i did not read the whole post i thought this was your question

 

[Iridescent]

sorry i did not read the whole post i thought this was your question

no problem

 

[ZaqZainab]

http://www.freeexampapers.com/index...IGCSE/Physics/CIE/2002 Jun/0625_s02_qp_01.pdf
question 18

 

[sourov97]

Q26.
Why is the answer C? According to me, it is supposed to be A.
Is it that with the bulbs connected in parallel, the resistance decreases. But when the bulb is removed, the resistance increases so the current decreases.

u r saying that the resistance has increased...so the current has decreased...then the ans is right!..C less than 2A

 

[Iridescent]

http://www.freeexampapers.com/index.php/directory/download?location=IGCSE/Physics/CIE/2002 Jun/0625_s02_qp_01.pdf
question 18

The answer is D.
This is because in the copper side, the heat is quickly conducted away so there is not much effect on the paper. But in the wood side, the heat is not conducted away which causes the browning of the paper.

 

[ZaqZainab]

The answer is D.
This is because in the copper side, the heat is quickly conducted away so there is not much effect on the paper. But in the wood side, the heat is not conducted away which causes the browning of the paper.

i thought copper is a good conductor so the paper should turn Brown
Thanks

 

[Iridescent]

u r saying that the resistance has increased...so the current has decreased...then the ans is right!..C less than 2A

First I thought it remains unchanged but later I understood why it is less than 2A.