Biology; Chemistry; Physics: Post your doubts here!

[Karim Nabil]

physics p6 2000-2001 qp-ms ?

 

[Mahnoorfatima]

http://papers.xtremepapers.com/CIE/Cambridge International O Level/Physics (5054)/5054_s10_qp_12.pdf
Question number 26? How do we know which switch to close?
In question 27 the answer is that if the length of the wire is decreased then the value of resistance wont change. How come that's possible ? shouldn't the answer be A? Because length is directly proportional to the resistance of a wire!
And question number 40!

 

[FLRNAB]

http://papers.xtremepapers.com/CIE/Cambridge International O Level/Physics (5054)/5054_s10_qp_12.pdf
Question number 26? How do we know which switch to close?
In question 27 the answer is that if the length of the wire is decreased then the value of resistance wont change. How come that's possible ? shouldn't the answer be A? Because length is directly proportional to the resistance of a wire!
And question number 40!

26 - It's like those maze puzzles. Just try to close a switch and see if it completes the circuit. Also the wires aren't connecting anywhere. If they were it would have been shown by a black dot.
27 - The question says "Which change will not reduce the value of the resistance of the wire?"
Only option which does not reduce the resistance is A. Here is simulation
40 - You can test the half lives using a calc. Try to get from 1200 to 150 in a duration of 3 minutes. So if half-life of 1 minute you get
1st Minute 1200/2 = 600
2nd Minute 600/2 = 300
3rd Minute 300/2 = 150

 

[exploded diper]

Y cant the answer be phosphorus or nitrogen............

 

[exploded diper]

To part c

 

[Faizan Muhammmad]

To part c

no idea
aluminium oxide is actually amphoteric
ms is wrong perhaps

 

[asadalam]

The ms is clearly wrong,the answer should be nitrogen!

 

[Mahnoorfatima]

NO is not acidic its neutral. While NO2 is acidic.

 

[Mahnoorfatima]

no idea
aluminium oxide is actually amphoteric
ms is wrong perhaps

But if you look at amphoteric oxides they can be seen as acidic as well as basic oxides. when they're reacting with acids they'll be known as acidic oxides. No? Not sure but its my perception.

 

[Mahnoorfatima]

http://papers.xtremepapers.com/CIE/Cambridge International O Level/Physics (5054)/5054_s10_qp_22.pdf
Question number 10. B part ii and iv. How do I calulate the number of pulses? I understand that one pulse is taking 1x10^-6 seconds. What next?
And in 4 what wil happen due to cracks??? And what will happen to the Pulses?

 

[funky brat]

http://papers.xtremepapers.com/CIE/Cambridge International O Level/Physics (5054)/5054_s10_qp_22.pdf
Question number 10. B part ii and iv. How do I calulate the number of pulses? I understand that one pulse is taking 1x10^-6 seconds. What next?
And in 4 what wil happen due to cracks??? And what will happen to the Pulses?

See that a pulse from S to S contains 6 dashes/marks. The distance between each mark is 1.0* 10^-6 seconds, so the time taken for one pulse (S to S) is 6* 10^-6. If one pulse takes 6* 10^-6 seconds then how many pulses can be there in 1 complete second. Apply unitary method and find the number of pulses.

When there are cracks some of the ultrasounds penetrate the cracks therefore the lines would be smaller than the actual pulses (S).

 

[funky brat]

But if you look at amphoteric oxides they can be seen as acidic as well as basic oxides. when they're reacting with acids they'll be known as acidic oxides. No? Not sure but its my perception.

When an amphoteric oxide is reacting with an acid,it would be known as basic oxide since acid + base = neutralisation and vice versa.

 

[funky brat]

how hydrogen carbonate reacts with CO2,what is the equation and why its product is yellow in color?

I haven't come across any such questions. :O
Which paper is this?

 

[funky brat]

View attachment 39429

in b(ii) y cant the ans be blood...the tissue tht is.....does blood contain high amoount of glucose...y o y

The answer would be muscle or liver tissue because they have the most concentration of glycogen.

 

[Haitam Banoori]

HELP!

Whats the difference between Period and wavelength of a wave? In theory its easy to remember. But on the graph its hard to know the difference!

 

[Haitam Banoori]

Another one. Where could I find good sources (notes) for electronics (introductory electronics, electronic systems) that relate to our syllabus?
And if someone can, what are; 1- REED RELAYS, 2- BISTABLE CIRCUITs, 3- ASTABLE CIRCUITs?

 

[Awesome12]

HELP!

Whats the difference between Period and wavelength of a wave? In theory its easy to remember. But on the graph its hard to know the difference!

When we have a displacement-time graph, the distance between 2 crests/troughs is the Time period
When we have a displacement-distance graph, the distance between 2 crests/troughs is the Wavelength

 

[Faizan Muhammmad]

But if you look at amphoteric oxides they can be seen as acidic as well as basic oxides. when they're reacting with acids they'll be known as acidic oxides. No? Not sure but its my perception.

it is simply impossible to be Al2O3
why?
look at the question it says the substance that reacts with oxygen and then acidic oxide is formed
Al2o3 is already reacted

 

[Faizan Muhammmad]

But if you look at amphoteric oxides they can be seen as acidic as well as basic oxides. when they're reacting with acids they'll be known as acidic oxides. No? Not sure but its my perception.

the name acidic basic or amphoteric is not decided by a single reaction
it is a property so even if it is reacting with acid it doesnt mean its basic the point is whether it reacts with both or not

 

[Faizan Muhammmad]

When an amphoteric oxide is reacting with an acid,it would be known as basic oxide since acid + base = neutralisation and vice versa.

the name acidic ,basic or amphoteric is not decided by a single reaction
it is a property so even if it is reacting with acid it doesnt mean its basic the point is whether it reacts with both or not