Physics, Chemistry and Biology: Post your doubts here!

[Awesome12]

Resistance can be thought of as an opposing force that would cause a decrease in current. So as temperature increases, the resistance decreases. An increase in temperature will allow more molecules in the substance/ conductor to become free and carry charges. Since there are more current carrying molecules produced, then resistance decrases.

i guess the info u read had made a mistake

Temperature is directly proportional to resistance. If you use a thin wire for your ac, it will burn out, because a large current flows, and since the wire is thin, more resistance occurs, causing it to burn

 

[Awesome12]

Please help me out here, I am attaching 2 photos here please find them.
Here is my question, first pic says that if Current increases the Resistance increases because Current increases the temperature and it in turn increases the Resistance
but in the second picture it says that if the Current increases the Resistance always decreases ... this got me really confused! please someone help me out

The second one seems to be wrong.
Voltage is not constant. In a series circuit, it is divided. In a parallel circuit, it is constant

 

[OneOfAKind]

The second one seems to be wrong.
Voltage is not constant. In a series circuit, it is divided. In a parallel circuit, it is constant

No, the statement means that what ever the condition of of the current or resistance shall be (low/high) the voltage delivered by the battery will be constant, so now sliding that matter away can you solve my doubt? ..

 

[Lola_sweet]

hey! winter

if its paper 11 of winter 2009 mcq 3 answer is D because the salt will be dissolve in water where as the sand wont thus you can remove sand by filter. and then when you evaporate the salt and water solution the water will evaporate of leaving the salt behind.
if its paper 12 of winter 2009 mcq 3 answer is C because after you mix the metal and acid you must filter to remove excess.

 

[ZohaKhan]

http://papers.xtremepapers.com/CIE/Cambridge International O Level/Physics (5054)/5054_w10_qp_41.pdf
Q.3
Can anyone pls solve ds up for meee n send me an attchmnt..... urgennnnnnnt :S

 

[ZohaKhan]

http://papers.xtremepapers.com/CIE/Cambridge International O Level/Physics (5054)/5054_s10_qp_41.pdf
Q4 a)i and a)ii ???

 

[exploded diper]

Resistance can be thought of as an opposing force that would cause a decrease in current. So as temperature increases, the resistance decreases. An increase in temperature will allow more molecules in the substance/ conductor to become free and carry charges. Since there are more current carrying molecules produced, then resistance decrases.

i guess the info u read had made a mistake

in the book it says tht since the resistance of the tungsten is high so it heats up more ( in electric kettles)
and then in tranmission wires you increase the voltage and hence the resistence so so less heat is lost.....explain

 

[Phoenix Blood]

Can you explain 4, (b) ?

 

[Phoenix Blood]

Explain how, Pl...

 

[Awesome12]

Explain how, Pl...

When we move the slider up, more resistance will occur across Q.
Since resistance is directly proportional to voltage, the voltage across it will increase. Voltage divides in a series circuit. We also know that the voltage supplied by the battery is constant. Thus the voltage across P will decrease

 

[Awesome12]

Can you explain 4, (b) ?

We are calculating the gravitational potential energy of the athlete. The height of the body is taken in to account with its centre of mass( in this case).
When we move a body up a hill, its centre of mass travels with it. In this case, the centre of mass has not risen by 2.0 meters. It has risen, but has not risen that significantly and is still less than 2.0 meters

 

[exploded diper]

We are calculating the gravitational potential energy of the athlete. The height of the body is taken in to account with its centre of mass( in this case).
When we move a body up a hill, its centre of mass travels with it. In this case, the centre of mass has not risen by 2.0 meters. It has risen, but has not risen that significantly and is still less than 2.0 meters

(adding).....since he is bendng so his cntre of mass is lowered

 

[OneOfAKind]

Resistance can be thought of as an opposing force that would cause a decrease in current. So as temperature increases, the resistance decreases. An increase in temperature will allow more molecules in the substance/ conductor to become free and carry charges. Since there are more current carrying molecules produced, then resistance decrases.

i guess the info u read had made a mistake

You're really confusing me! till yet I was pretty sure if temprature increases resistance increases!

 

[peacce]

http://papers.xtremepapers.com/CIE/Cambridge International O Level/Physics (5054)/5054_s11_qp_21.pdf
Q10 allllll parrttts

http://papers.xtremepapers.com/CIE/Cambridge International O Level/Physics (5054)/5054_s11_qp_21.pdf

Q11 ciii

 

[3abder7man]

center of mass i

We are calculating the gravitational potential energy of the athlete. The height of the body is taken in to account with its centre of mass( in this case).
When we move a body up a hill, its centre of mass travels with it. In this case, the centre of mass has not risen by 2.0 meters. It has risen, but has not risen that significantly and is still less than 2.0 meters

Just a little correction, center of mass is the one always used, not just in this case.

 

[Phoenix Blood]

How are the answers as such?

 

[Phoenix Blood]

Why shouldn't it be completely refracted?

 

[Phoenix Blood]

How to get about?

 

[Phoenix Blood]

Why can't it be conc. NaCl solution plainly too?

 

[exploded diper]

http://papers.xtremepapers.com/CIE/Cambridge International O Level/Physics (5054)/5054_s11_qp_21.pdf
Q10 allllll parrttts

http://papers.xtremepapers.com/CIE/Cambridge International O Level/Physics (5054)/5054_s11_qp_21.pdf
1200*2=2400,2400*2=4800.......as the half life is 15 hours so the original countrate must have been doubled for 15 hours and thn doubled agn for the other 15 hours to make 30hours.............as it asked vat the rate was (before) the start of the experiment.......
Q11 ciii