Physics, Chemistry and Biology: Post your doubts here!

[youstina]

i have doubt in ionic equation .

 

[étudiante]

i have doubt in ionic equation .

what about them do you find confusing?

To form ionic equations, just write out all the reactants and products as ions with their charges and states... cancel the ones that have the same charge and state fom either side of the equation... the remaining gives you the ionic equation

 

[IGCSE STUDENT]

ok, I need help in Physics, May/June 2006 paper 3, question 4 (c). Can anyone help please Thank you in advance

 

[Yours Truly]

ok, I need help in Physics, May/June 2006 paper 3, question 4 (c). Can anyone help please Thank you in advance

Answer:

E = Power * Time = Pt
E = Mass * Latent heat of vaporization = mL

mL = Pt
L = (Pt)/m


Power is given as 120 W
Per second means 1 second. So, Time = 1s
Mass = 0.05g

Replace values in equation:

L = (120 * 1)/0.05
L = 2400 J/g

 

[IGCSE STUDENT]

Answer:

E = Power * Time = Pt
E = Mass * Latent heat of vaporization = mL

mL = Pt
L = (Pt)/m


Power is given as 120 W
Per second means 1 second. So, Time = 1s
Mass = 0.05g

Replace values in equation:

L = (120 * 1)/0.05
L = 2400 J/g

Thank you so much, I understand it now

 

[beewhiz997]

can someone explain specific latent heat of vaporisation to me? and the difference between motors and generators

 

[étudiante]

can someone explain specific latent heat of vaporisation to me? and the difference between motors and generators

Specific latant heat of vapourisation is the amount of energy required to convert 1 kg of a liquid into a vapour.

motors use electricity and do mechanical work, Generators use mechanical energy to produce electricity... they are kind of opposite to each other.
In motors, the magnets interact with the current in the wire and cause the coil to rotate (mechanical work). In generators, the rotation of the coil causes electrons to pushed thru an outer circuit (ie current is produced).

 

[Yousif Mukkhtar]

Guys, I have a slight doubt here. Can some one explain these portions of the syllabus for me:
Use a hand lens to identify and describe the anthers and stigmas of one, locally available, named, wind-pollinated flower, and examine the pollen grains under a light microscope or in photomicrographs.

 

[Kareem Gamal Omar]

what is the role of lymphatic system? in matter of fact I DONT UNDERSTAND THE LYMPHATIC SYSTEM!

 

[JOEJOE]

CHEM:

HOW TO DRAW THE DOT CROSS DIAGRAM FOR AN AMMONIUM ION!?!

 

[étudiante]

CHEM:

HOW TO DRAW THE DOT CROSS DIAGRAM FOR AN AMMONIUM ION!?!

remeber dat the fourth bond is dative covalent so u need 2 show it as an arrow...

and put it in brackets with a sigle positive charge shown....

 

[Moar]

In physics:
Do we look at direction of current as conventional or actual? This just confuses me when i would like to mark an answer according to that.

 

[étudiante]

In physics:
Do we look at direction of current as conventional or actual? This just confuses me when i would like to mark an answer according to that.

Conventional when marking in circuits and stuff...

 

[AAnsarii]

In physics:
Do we look at direction of current as conventional or actual? This just confuses me when i would like to mark an answer according to that.

You look at d conventional current, dat's what my sir says
All d best!

 

[AAnsarii]

remeber dat the fourth bond is dative covalent so u need 2 show it as an arrow...

and put it in brackets with a sigle positive charge shown....

What's dat??

 

[étudiante]

What's dat??

a dative covalent bond is one in which both the shared electrons come from the same atom (in this case, Nitrogen)

 

[SALT]

do beta particles hav mass??

 

[étudiante]

do beta particles hav mass??

beta particles are electrons so they have the same mass as an electron...
generally in most cases though, we ignore it because the mass of the beta particle is VERY small compared to the rest of the particles involved...

 

[Moar]

Help in physics : Paper 1 june 2010 http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Physics (0625)/0625_s10_qp_13.pdf
For question 24 i know C is the right answer but not so sure why ?Also in question 34 why is electric fire a wrong answer?

 

[AAnsarii]

Help in physics : Paper 1 june 2010 http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Physics (0625)/0625_s10_qp_13.pdf
For question 24 i know C is the right answer but not so sure why ?Also in question 34 why is electric fire a wrong answer?

The explanation may be as follows:
u must noe dat rays cross at d lens in a camera, dat's what i think, n sby plz correct me if im wrong
n about d fire, how will a fire take place?? im really askin, plz reply
All d best