Biology; Chemistry; Physics: Post your doubts here!

[Saad Mughal]

im applying tht reversible reaction theory here.. if more resistance means more temperature, then already more temperature will mean less resistance. Saad Mughal usama321

No, higher temperature = higher resistance.

 

[Saad Mughal]

i did the same in question no.4 but the marking scheme says 9.0g/cm3

I read the question again, it says mass of each steel ball is 27 g. So, we have to multiply by 10 as well.

 

[bubbles1997]

The higher the amplitude of a sound, the louder it is. If you shout, the amplitude of the sound is high whereas if you whisper, the amplitude is low.
If the frequency is high, then the pitch is also high, and vice versa, pitch pitch can be taken from the screeching sound that some animals make whereas low pitch is when you have a sore throat.

That was OUTSTANDING description... your're super! Thanks...!!!

 

[usama321]

Does the induced current in the coil in ac generator depend on the resistance of the coil? does the induced emf remain constant and the current decreases if we increase the resistance of the turning coil?

 

[TheStallion-Reborn]

Does the induced current in the coil in ac generator depend on the resistance of the coil? does the induced emf remain constant and the current decreases if we increase the resistance of the turning coil?

seems legit..

 

[bubbles1997]

describe the use of a ripple tank to show
(1) reflection at a plane surface,
(2) refraction due to a change of speed at constant frequency.

 

[usama321]

Does the induced current in the coil in ac generator depend on the resistance of the coil? does the induced emf remain constant and the current decreases if we increase the resistance of the turning coil?

what do you say Saad Mughal? i think i read somewhere the resistance does not affect it?

 

[Saad Mughal]

Not sure Usama. I'll get back to you on this.

 

[bubbles1997]

explain how the loudness and pitch of sound waves relate to amplitude and frequency?

 

[Saad Mughal]

explain how the loudness and pitch of sound waves relate to amplitude and frequency?

I told you, loudness is affected by the amplitude of a sound wave (no effect by frequency).
Pitch is affected by the frequency of a sound wave (no effect by amplitude).

 

[iamLbert]

4. (b) (ii) Why the evaporation of a liquid cools the liquid? [2]
4. (b) (iii) Why the rate of evaporation is greater when a liquid is hotter? [2]
Source : 5054/02/M/J/09 OL paper

 

[sourov97]

4. (b) (ii) Why the evaporation of a liquid cools the liquid? [2]
4. (b) (iii) Why the rate of evaporation is greater when a liquid is hotter? [2]
Source : 5054/02/M/J/09 OL paper

(ii) evaporation causes some of the most high energetic molecules to leave the liquid leaving low energetic ones behind...hence the liquid cools!

 

[sourov97]

4. (b) (ii) Why the evaporation of a liquid cools the liquid? [2]
4. (b) (iii) Why the rate of evaporation is greater when a liquid is hotter? [2]
Source : 5054/02/M/J/09 OL paper

(iii) in hotter liquids there are more high energetic molecules which leave the liquid faster by breaking the attraction force between them!

 

[farhan141]

(ii) evaporation causes some of the most high energetic molecules to leave the liquid leaving low energetic ones behind...hence the liquid cools!

(i) Evaporation of a liquid cools the liquid because the high energy molecules on the surface of the liquid escape which makes the liquid cooler as the less energy molecules are left behind.

(ii) The rate of evaporation is greater because there are more high energy molecules when the liquid is hotter and this allows the rapid evaporation of the liquid.

 

[Sami Imran]

(i) Evaporation of a liquid cools the liquid because the high energy molecules on the surface of the liquid escape which makes the liquid cooler as the less energy molecules are left behind.

(ii) The rate of evaporation is greater because there are more high energy molecules when the liquid is hotter and this allows the rapid evaporation of the liquid.

for (iii) u need to mention the force of attraction being broken!..[2]

 

[farhan141]

Ok

 

[Saad Mughal]

4. (b) (ii) Why the evaporation of a liquid cools the liquid? [2]
4. (b) (iii) Why the rate of evaporation is greater when a liquid is hotter? [2]
Source : 5054/02/M/J/09 OL paper

-Evaporation is the process in which the more energetic molecules break the forces of attraction of the body and leave the liquid, this leaves behind less energetic molecules hence the liquid becomes cooler.
-When the liquid is hotter, there are more high energy molecules that break the forces of the attraction of the body and escape from the liquid, therefore, the higher the temperature of the liquid, the higher the rate of evaporation.

 

[bubbles1997]

I told you, loudness is affected by the amplitude of a sound wave (no effect by frequency).
Pitch is affected by the frequency of a sound wave (no effect by amplitude).

Well may be i am misunderstanding. the question asked is from the syllabus... page 23
http://papers.xtremepapers.com/CIE/Cambridge International O Level/Physics (5054)/5054_y13_sy.pdf

 

[Saad Mughal]

Well may be i am misunderstanding. the question asked is from the syllabus... page 23
http://papers.xtremepapers.com/CIE/Cambridge International O Level/Physics (5054)/5054_y13_sy.pdf

Yeah, they've asked us what affects do AMPLITUDE and FREQUENCY have on loudness and pitch.

 

[papajohn]

Anyone please explain me.. Answer will be appreciated.