Biology; Chemistry; Physics: Post your doubts here!

[asadalam]

Isn't that for proving that transpiration occurs most at the bottom of the leaf?

And transpiration occurs through stomata so where it occurs,there the stomata will be.

 

[asadalam]

Hei guys.Can anyone help me with this terribly hard question from may june 13 paper.Thank u.

Is this IGCSE

 

[periyasamy]

Is this IGCSE

I am sorry didnt realise this is only forIGSE.haha...

 

[exploded diper]

I am sorry didnt realise this is only forIGSE.haha...

I don't think this is igcse....Is this igcse

 

[exploded diper]

This is not I am sure

 

[princess sofia]

IT WAS;
Q- 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- REEDRELAYS, 2- BISTABLE CIRCUITs, 3- ASTABLE CIRCUITs?

Reed n relays can b found in electromagnetics . They work on the principle of electromagnetic induction . As the current passes on coil becomes magnetised n attract da other , thus completing da circut
I have no idea abt da other 2 , if u found so do tell me as well
Hope it helped

 

[Karim Nabil]

Reed n relays can b found in electromagnetics . They work on the principle of electromagnetic induction . As the current passes on coil becomes magnetised n attract da other , thus completing da circut
I have no idea abt da other 2 , if u found so do tell me as well
Hope it helped

A bistable circuit is a sort of electronic switch: it may use fancy logic, but ultimately it is just a switch that has two 'states', like on and off, or bright and dim. And there is a way that the circuit can be set to one 'state' or the other. So maybe when it is dark in the room, the switch is set make the television screen dimmer, and when it is light, the screen gets brighter. Or a night-light comes on when it is dark in the room. Some condition has to change to make anything happen. Maybe a person throws a switch. A light-switch is a simple bistable circuit.

An astable circuit is one that is going from one state to the other, back and forth, constantly. Lets say it is going on and off, and on and off. it does not need to be turned on and of. That is part of the circuit itself.

That does not mean that the length of the 'on' is the same as the length of the 'off', but it does mean that it never stops switching back and forth. A flashing light is like that. And the 'clock' that makes your computer do 3,000,000,000 logic steps a second (3 gigahertz) is that kind of circuit.
#copied

 

[princess sofia]

A bistable circuit is a sort of electronic switch: it may use fancy logic, but ultimately it is just a switch that has two 'states', like on and off, or bright and dim. And there is a way that the circuit can be set to one 'state' or the other. So maybe when it is dark in the room, the switch is set make the television screen dimmer, and when it is light, the screen gets brighter. Or a night-light comes on when it is dark in the room. Some condition has to change to make anything happen. Maybe a person throws a switch. A light-switch is a simple bistable circuit.

An astable circuit is one that is going from one state to the other, back and forth, constantly. Lets say it is going on and off, and on and off. it does not need to be turned on and of. That is part of the circuit itself.

That does not mean that the length of the 'on' is the same as the length of the 'off', but it does mean that it never stops switching back and forth. A flashing light is like that. And the 'clock' that makes your computer do 3,000,000,000 logic steps a second (3 gigahertz) is that kind of circuit.
#copied

thnx

 

[Karim Nabil]

thnx

you're welcome!

 

[Awesome12]

What is reflux?

 

[Dark Destination]

What is reflux?

I think it means heating using a condenser on top, to prevent gaseous vapors from escaping.

 

[Awesome12]

I think it means heating using a condenser on top, to prevent gaseous vapors from escaping.

like in fractional distillation?

 

[Dream.Eater]

like in fractional distillation?

Heating by reflux is a technique used in oxidation of alcohols and esterification. It involves a vertical condenser(water in from bottom and out from top) to condense the volatile alcohols so that the reaction will proceed. A special type of heater called a Heating Mantle is used since alcohols are highly flammable and the reaction goes on for hours since its extremely slow(esterification can take like 4hrs or more).

However Ive noticed that in questions where they ask for conditions for oxidation,esterification,... saying ''Heating by reflux'' is awarded a mark.

 

[Dark Destination]

Heating by reflux is a technique used in oxidation of alcohols and esterification. It involves a vertical condenser(water in from bottom and out from top) to condense the volatile alcohols so that the reaction will proceed. A special type of heater called a Heating Mantle is used since alcohols are highly flammable and the reaction goes on for hours since its extremely slow(esterification can take like 4hrs or more).

However Ive noticed that in questions where they ask for conditions for oxidation,esterification,... saying ''Heating by reflux'' is awarded a mark.

What if we write ''Warm'' instead of Reflux, as a condition?

 

[Dream.Eater]

What if we write ''Warm'' instead of Reflux, as a condition?

I don't think a mark is given for 'warm' alone unless you mention about the vertical condenser, mantle and so on. By saying heat by reflux you're implying the entire heating procedure so you can guarantee the mark....

 

[Dream.Eater]

Awesome12 Dark Destination and anyone else who can help me.....
What is the difference between codominance and incomplete dominance?

 

[Awesome12]

Awesome12 Dark Destination and anyone else who can help me.....
What is the difference between codominance and incomplete dominance?

In co-dominace, both alleles express their traits. For example, if we crossed a black chicken with a white chicken, the result would be a chicken having black skin with white spots (or vice versa)
In incomplete dominance, none of the alleles express their traits. Instead, the offspring has an allele that is somewhat intermediate between the two alleles. For example, a flower with red flowers is crossed with a flower with white flowers. The offspring will have pink flowers

 

[Dream.Eater]

In co-dominace, both alleles express their traits. For example, if we crossed a black chicken with a white chicken, the result would be a chicken having black skin with white spots (or vice versa)
In incomplete dominance, none of the alleles express their traits. Instead, the offspring has an allele that is somewhat intermediate between the two alleles. For example, a flower with red flowers is crossed with a flower with white flowers. The offspring will have pink flowers

So they're not the same thing...
Thanks bro!

 

[exploded diper]

explain thoroughly the nitrogen cycle.......and its importance........

 

[funky brat]

Guys what exactly is a half-life? For example if I have a bag containing a piece of a radioactive element which has 10,000 atoms in it. It's half life is say, 10 minutes. So what would happen after 10 minutes? The number of atoms in the bag will be reduced to 5000 atoms OR the nuclei of those 10,000 atoms contains half the original number of alpha, beta and gama rays?