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Physics, Chemistry and Biology: Post your doubts here!

princess sofia

princess sofia

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can any 1 tell me dat wt happens in a capacitor , c I know dat its used to store energy , tell me if I m rite dat the (-)ive terminal repels the electrons to one plat whereas (+)ive terminal attracts electrons 4m other plate , and like thx d capacitor stores electricity
 
Nabeel.Ahmad

Nabeel.Ahmad

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Iridescent said:
That is not in the IGCSE syllabus. You will study that once you go into the field of Theoretical Physics.
Click to expand...

Okay, Thanks for clearing that up.
I was really tensed about this topic. But now i know that its not in the IGCSE syllabus, that's a relief. :)
 
Iridescent

Iridescent

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Nabeel.Ahmad said:
Okay, Thanks for clearing that up.
I was really tensed about this topic. But now i know that its not in the IGCSE syllabus, that's a relief. :)
Click to expand...

Yes. The brain of IGCSE is under-developed to understand the complex phenomena of Iridescence.
You're welcome. :)
 
princess sofia

princess sofia

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guyz how the hell r we gonna find that how long will it take a 50W heater to melt 100g of ice at 0 degrees
 
Iridescent

Iridescent

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Umar Ahmed said:
Have a doubt in this question can anyone help me

The half-life of a radioactive substance is 5 hours. A sample is tested and found to contain 0.48 g
of the substance.
How much of the substance was present in the sample 20 hours before the sample was tested?
A 0.03 g
B 0.12 g
C 1.92 g
D 7.68 g
Click to expand...

The answer is D.
Before 5 hours, the sample was, 0.48 *2 = 0.96g.
Before 10 hours, 0.96 * 2 = 1.92g
Before 15 hours, 1.92 * 2 = 3.48g
Before 20 hours, 3.48 * 2 = 7.68g.
 
Nabeel.Ahmad

Nabeel.Ahmad

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princess sofia said:
guyz how the hell r we gonna find that how long will it take a 50W heater to melt 100g of ice at 0 degrees
Click to expand...


First we need to figure out how much heat energy does 100g of Ice need in order to melt.
In order to melt, a solid needs to absorb a certain amount of Energy that will be used to overcome the forces of attraction, in order for it to change its state and melt.
The Latent Heat of Fusion of ''Water/Ice''.. is 334 J/g.
So, this means that 1g of Ice, needs to absorb 334 J of Energy in order for it to melt and become water.

To find out how much Heat is required by 100g of ice to melt, we use the formula:

L = m x l.
[L = Heat required to melt]
[m = Mass in g]
[l = Latent Heat of Fusion]

So the heat required to melt 100 g of Ice can be calculated:

L = 100 g x 334 J/g = 33,400 J.

Now that we have finalized how much heat energy is required, we need to move on to how much time will be taken to provide that energy.
The energy will be supplied by a Heater.
Heaters always have some degree of Power, in Watt.
So a Heater of 50 Watt supplies 50 Joules of Energy per Second.
That's why it is called a 50 Watt Heater.

Power = Energy Supplied / Time Taken to Supply that energy.

We know that a 50 Watt Heater has to supply 33,400 Joules of Energy to 100g of Ice.. in order to melt it.

P = E/t
t = E/P
t = 33,400/50
= 668 seconds.
So the 50 Watt Heater will supply 33,400 Joules of Energy in 668 seconds, to 100g of Ice, in order to melt it.

If you understand all of the above, next time you can use a quicker formula.

Pt = ml
50 Watt * t = 100g * 334 J/g
t = 668 seconds.
 
princess sofia

princess sofia

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Nabeel.Ahmad said:
First we need to figure out how much heat energy does 100g of Ice need in order to melt.
In order to melt, a solid needs to absorb a certain amount of Energy that will be used to overcome the forces of attraction, in order for it to change its state and melt.
The Latent Heat of Fusion of ''Water/Ice''.. is 334 J/g.
So, this means that 1g of Ice, needs to absorb 334 J of Energy in order for it to melt and become water.

To find out how much Heat is required by 100g of ice to melt, we use the formula:

L = m x l.
[L = Heat required to melt]
[m = Mass in g]
[l = Latent Heat of Fusion]

So the heat required to melt 100 g of Ice can be calculated:

L = 100 g x 334 J/g = 33,400 J.

Now that we have finalized how much heat energy is required, we need to move on to how much time will be taken to provide that energy.
The energy will be supplied by a Heater.
Heaters always have some degree of Power, in Watt.
So a Heater of 50 Watt supplies 50 Joules of Energy per Second.
That's why it is called a 50 Watt Heater.

Power = Energy Supplied / Time Taken to Supply that energy.

We know that a 50 Watt Heater has to supply 33,400 Joules of Energy to 100g of Ice.. in order to melt it.

P = E/t
t = E/P
t = 33,400/50
= 668 seconds.
So the 50 Watt Heater will supply 33,400 Joules of Energy in 668 seconds, to 100g of Ice, in order to melt it.

If you understand all of the above, next time you can use a quicker formula.

Pt = ml
50 Watt * t = 100g * 334 J/g
t = 668 seconds.
Click to expand...
THNX N SO WE HAVE TO LEARN THE AMOUNT OF HEAT REQUIRED AS IT IS NOT GIVEN IN THE QUESTION
 
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