Physics, Chemistry and Biology: Post your doubts here!

[Sahil_M]

But if S1 was closed...then without doubt both lamps would be on as the current would flow through the base current in the transistor so the circuit would be complete...if s1 was open no current would flow throughout to the base in the transistor so the circuit wont be complete...both lamps would be off....that's wat I think

 

[Nita Mahajan]

That was a trick question...the answer was only relates to switch S1...if it was open then both lamps are off...if closed then both are on...so the answer was OFF OFF and ON ON

Yes!!!! i wrote that!!! wow!

 

[Arshan]

yes u r rite........
but it says s1 open then it would be off
and s2 closed so lamp would be on......
i wrote..... OFF ON AND ON OFF......

 

[islam nael]

i want to get topicw wise pastpaper for chem ,phy, and bio............................can u help please

 

[Xtremeist]

chem winter 2011 multichoice qp 13 question 33

 

[Love Islam]

Ppl I’m in so much big trouble ..I know the formulas of electricity Chap
but I don’t know when I’m suppose to use the formula on the given Question !!
(Physics 0625) they r so confusing !!

 

[N.M]

Ppl I’m in so much big trouble ..I know the formulas of electricity Chap
but I don’t know when I’m suppose to use the formula on the given Question !!
(Physics 0625) they r so confusing !!

Aoa wr wb,

At the beginning what you can do is that write all the formulas at the corner of the paper b4 starting the question. Then carefully read the question and copy down the given info (like P.d=20V n etc...) once you have the data in front of you, u can simply match it with the formulas you have written... N then just plug in the values n solve it.

This is how I used to do initially then by tym n practice you learn the formulas, n know which formula is applicable on which question...

 

[To2a Bahaa]

Guysss ! In electrolysis, when the remaining solution is an acid or a base where is it depostited? Cathode or anode? There are questions in paper 1 ...

 

[examkiller]

In some questions of physics paper 1, it says that " a simple mercury barometer. The barometer is reading is H cm of mercury.
What is the pressure at S ( the top , air part ) ? Ans says Approx. zero. why is it zero and not atmospheric presssure ?
question is p.1 m.j.2004
thnks

 

[Ahmed Nasser]

Guys whats the difference between Beaker, Burette, Conical flask, Measuring cylinder and pipette??

 

[Shepard97]

Beaker is just a container..
Burette is a vertical cylinder piece,.. also helps in measuring volume of the substance.. ( liquid)
Conical Flask , another type of container .. has readings on it's circumference..
Measuring Cylinder , used to measure volume ,
Pipette, used to transport a measured volume of liquid.

 

[Shepard97]

Guysss ! In electrolysis, when the remaining solution is an acid or a base where is it depostited? Cathode or anode? There are questions in paper 1 ...

Hmmm..
It depends on ions present in solution .
For example , if it is Chlorine... as we know .. chlorine has a negative charge of -1 .. so it would deposit on positive rod . which is Anode
and if a substance has a positive charge.. it is deposited on the Cathode ( the negative rod)

 

[To2a Bahaa]

Hmmm..
It depends on ions present in solution .
For example , if it is Chlorine... as we know .. chlorine has a negative charge of -1 .. so it would deposit on positive rod . which is Anode
and if a substance has a positive charge.. it is deposited on the Cathode ( the negative rod)

Thanks alot This means if it's Na0H since Na+ is present, it's deposited at the cathode and if H2SO4.. since SO42- is present, it is deposited at the anode?

 

[Shepard97]

Y

Thanks alot This means if it's Na0H since Na+ is present, it's deposited at the cathode and if H2SO4.. since SO42- is present, it is deposited at the anode?

Yup
it always depends on the charge on the ions...
You understood xD

 

[Ahmedm96]

http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Physics (0625)/0625_w07_qp_1.pdf

no.34 not contented by the ms answer

 

[VelaneDeBeaute]

http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Physics (0625)/0625_w07_qp_1.pdf

no.34 not contented by the ms answer

If you don't see why A is the correct one, try figuring out why other options are wrong.
Lets see then.
B is wrong, because thicker insulation would definitely stop heat escaping but this is what would lead to overheating of the cable and we don't want that.
C is wrong, because more resistance would lead to more heat being produced and heat loss cannot be countered by a thinner insulation. Plus, the cable has to be used for a mains circuit so using thinner insulation is a not appropriate.
D is wrong, because thinner insulation would allow more heat to escape, not less heat.
That leaves us with A. If you consider that now, a cable with less resistance would not allow overheating as well as the thicker insulation would ensure safety in the mains. Hence, it is correct

 

[Shepard97]

If you don't see why A is the correct one, try figuring out why other options are wrong.
Lets see then.
B is wrong, because thicker insulation would definitely stop heat escaping but this is what would lead to overheating of the cable and we don't want that.
C is wrong, because more resistance would lead to more heat being produced and heat loss cannot be countered by a thinner insulation. Plus, the cable has to be used for a mains circuit so using thinner insulation is a not appropriate.
D is wrong, because thinner insulation would allow more heat to escape, not less heat.
That leaves us with A. If you consider that now, a cable with less resistance would not allow overheating as well as the thicker insulation would ensure safety in the mains. Hence, it is correct

Explained in detail... nice

 

[Ibtizam]

I don't understand moments at all

 

[Shepard97]

Hmm..
See.. a moment is FORCE multiplied by DISTANCE FROM PIVOT.... generally.. this is the case..
there are 2 types of moments Anti-Clockwise Moments and Clockwise Moments..
And... Anti-clockwise moments is always equal to Clockwise moments

 

[Purple@white]

In a species of plant, the allele for red flowers (R) is dominant over the allele for white flowers (r).
Two red–flowered plants were crossed.
plant with red flowers × plant with red flowers = 93 red-flowered and 28 white-flowered

What are the genotypes of the parents?
A. RR and rr
B. RR and Rr
C. Rr and Rr
D. Rr and rr
urgent!!! plz reply ASAP!!!! THANKS!!!!