Biology; Chemistry; Physics: Post your doubts here!

[Tharindu]

The student was provided with a thermometer, a stopwatch and a beaker.

Stopwatch can be used to note the TIME
Thermometer can be used to get a reading of the TEMPERATURE
While the beaker is good for nothing

A consists of "Mass" and "Volume
B consists of "Mass" and "Temperature"
C consists of "Volume" and "Time"
D consists of "Temperature" and "Time" and so is the right answer (as we can only measure the TIME and TEMPERATURE accurately)

this was not the question I asked

 

[Tharindu]

this was not the question I asked

It's question 2....Mcq chemistry 2011 oct November....Paper 11

 

[GetSomeLife]

this was not the question I asked

Sorry my bad

The labels fell off two bottles each containing a colorless solution, one of which was sodium
carbonate solution and the other was sodium chloride solution.
The addition of which solution to a sample from each bottle would most readily enable the bottles
to be correctly relabelled?
A ammonia
B hydrochloric acid
C lead(II) nitrate
D sodium hydroxide

A: Ammonia (as per the syllabus) will not react with either one and so is out of the question.
B: HCl will immediately react with Na2CO3 releasing CO2 and while it won't react with NaCl (therefore, is the right answer)
C: It can also distinguish between the 2 compounds by producing a white precipitate with the NaCl but is not as fast and readily available in comparison with HCl
D: I can't differentiate between them as both contain the same cation "Na"

 

[GetSomeLife]

It's question 2....Mcq chemistry 2011 oct November....Paper 11

Yeah i figured... i checked the wrong course (i.e. IGCSE)

 

[Rimsa]

-whats a diode?
-at high voltage, whats more safer? AC current or DC current?
-are transmission line thinner with lower current?
- n physics, june05, p12, q37

 

[ashiqbal]

-whats a diode?
-at high voltage, whats more safer? AC current or DC current?
-are transmission line thinner with lower current?
- n physics, june05, p12, q37 (attached below)View attachment 7637

diode allows current to flow in only one direction.
at high voltage, both AC and DC are dangerous
yes, transmission lines can be made thinner with lower current
(C) 60 degrees. this is because we know that the current is same in series circuit. and if voltage in V is 2V, voltage across 3000 ohm will be 4V. we can calculate current by V/R = 4/3000 = 0.00133. then we will divide 2V by 0.00133 to get 1500 ohm. match the value of 1500 from graph to 60 degrees

 

[étudiante]

in dry cell battery energy is converted from chemical ----->electrical ????
in light emission diode energy is converted from light ----> electrical ????
in microphone from sound -----> electrical ????
and what's conversion of energy in photo-emissive cell . please confirm above to me !

@battery.. yes
@LED... its electrical -----> light (led stands for light EMITTING diode)
@microphone... yes..

 

[stareaj]

can someone pls explain mcq 1 ,2 ,3 ,21 ,26, 30, 33, 35 of chemistry paper 1 oct nov 2011 pls asap i dont get this at allllll

 

[convent2012]

can someone pls explain mcq 1 2 3 21 26 30 33 35 of chemistry paper 1 oct nov 2011 pls asap i dont get this at allllll

11 or 12 ???

 

[stareaj]

11 or 12 ???

1 and 2

 

[Mayedah]

Can anybody plz tell me the weightage each of paper 1, paper 2 ,and atp paper for overall percentage !

 

[Rimsa]

Can anybody plz tell me the weightage each of paper 1, paper 2 ,and atp paper for overall percentage !

refer to the syllabus of concerned subject

 

[ahmed kalim khan niazi]

Dear Friends From where i can get tips to plot graphs
for biology atp paper
when we have to make line, bar and curve graph

 

[Dukeofwin]

BIOLOGY!

Please tell me the exact way of how to find magnification?
(The exact way means how we have to write in exams)

Take Actual length=6mm
And Drawing length=12mm

 

[ashiqbal]

BIOLOGY!

Please tell me the exact way of how to find magnification?
(The exact way means how we have to write in exams)

Take Actual length=6mm
And Drawing length=12mm

write --> Image (drawn) length/actual length = 12/6 = x2
dont forget to write the times symbol (x) before magnification.
if the actual image is already magnified, eg. x500, then you will have to do like this -->(12/6) * 500 = x1000

 

[Spidey21]

diode allows current to flow in only one direction.
at high voltage, both AC and DC are dangerous
yes, transmission lines can be made thinner with lower current
(C) 60 degrees. this is because we know that the current is same in series circuit. and if voltage in V is 2V, voltage across 3000 ohm will be 4V. we can calculate current by V/R = 4/3000 = 0.00133. then we will divide 2V by 0.00133 to get 1500 ohm. match the value of 1500 from graph to 60 degrees

both are dangerous at high voltage but i think at high voltage AC is safer...

 

[amna shah]

WHAT IS INTERNAL ENERGY ?? IM VERY CONFUSED WHEN IM READING THE MARKING SCHEMES OF THE QUESTIONS IN WHICH WE HAVE TO DESCRIBE THE TOTAL ENERGY CONVERSION, MOST OF THE TIME THE ENERGIES END UP AS INTERNAL ENERGY .. PLEASE EXPLAIN HOW AND WHEN DOES THIS HAPPEN ... GIVE AN EXAMPLE IF YOU CAN .. THANKS

 

[multixamza01]

WHAT IS INTERNAL ENERGY ?? IM VERY CONFUSED WHEN IM READING THE MARKING SCHEMES OF THE QUESTIONS IN WHICH WE HAVE TO DESCRIBE THE TOTAL ENERGY CONVERSION, MOST OF THE TIME THE ENERGIES END UP AS INTERNAL ENERGY .. PLEASE EXPLAIN HOW AND WHEN DOES THIS HAPPEN ... GIVE AN EXAMPLE IF YOU CAN .. THANKS

Kinetic Energy + Potential Energy = Internal Energy

Example :
When a Solids heated . The Particles gain kinetic energy and move more vigorously . Therefore their kinetic energy increases . The constant collision with neighboring particles increases the separation between them (potential energy increases ). As both Kinetic and Potential increase their sum (internal energy) also increases.

So when the Marking scheme says internal energy it refers to either kinetic or potential energy .

Hope this helped

 

[amna shah]

YEAH IT HELPED A LOT THANKS ...

SO IF A CAR GOES UP FROM REST A HILL AND DOWN AND STOPS, WHAT WILL BE THE TOTAL ENERGY CHANGE ?

 

[multixamza01]

YEAH IT HELPED A LOT THANKS ...

SO IF A CAR GOES UP FROM REST A HILL AND DOWN AND STOPS, WHAT WILL BE THE TOTAL ENERGY CHANGE ?

kinetic ----> potential ----> kinetic----> heat and sound

in short : internal energy ----> heat and sound