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Physics, Chemistry and Biology: Post your doubts here!

Iridescent

Iridescent

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1. The answer is B because at the left side, the water coming is at room temperature. Even, if the flow is increased, the temperature of the water is still the same i.e., room temperature. At the right side, the water coming has been heated up by the heater. If the flow of water increases, there is less time for the heater to heat the water. So, the reading on the thermometer goes down.

2.The cable has been designed to work with 3A current. If the fuse is 13A, it will allow current of more than 3A. So if current more than 3A flows, the cable will overheat which can melt the insulation.

3. The motor will rotate slowly because the rate of flow of charge through it is less i.e., the voltage is less.

4. Half-life of a radioactive isotope is the time taken for the activity of any given sample to decay to half its original value. As the half-life is 6000 years, after 6000 years the count rate will be 4000/2 = 2000 counts/minute. after another 6000 years, it will be 2000/2 = 1000 counts/minute. Thus, after 12000 (6000+6000) years it will be 1000 counts/minute.

Hope you got it :)
 
GorgeousEyes

GorgeousEyes

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Iridescent said:
1. The answer is B because at the left side, the water coming is at room temperature. Even, if the flow is increased, the temperature of the water is still the same i.e., room temperature. At the right side, the water coming has been heated up by the heater. If the flow of water increases, there is less time for the heater to heat the water. So, the reading on the thermometer goes down.

2.The cable has been designed to work with 3A current. If the fuse is 13A, it will allow current of more than 3A. So if current more than 3A flows, the cable will overheat which can melt the insulation.

3. The motor will rotate slowly because the rate of flow of charge through it is less i.e., the voltage is less.

4. Half-life of a radioactive isotope is the time taken for the activity of any given sample to decay to half its original value. As the half-life is 6000 years, after 6000 years the count rate will be 4000/2 = 2000 counts/minute. after another 6000 years, it will be 2000/2 = 1000 counts/minute. Thus, after 12000 (6000+6000) years it will be 1000 counts/minute.

Hope you got it :)
Click to expand...
I understood everything except the forth question . I have a problem with half life always
I don't get it at all ..thankk you a loot :)
 
Iridescent

Iridescent

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GorgeousEyes said:
I understood everything except the forth question . I have a problem with half life always
I don't get it at all ..thankk you a loot :)
Click to expand...
If the original value is 'x', in the first half-life the no. of counts remaining will be x/2. In the next half-life, it will be half of x/2 i.e., x/4. In the next half-life, it will be half of x/4 i.e., x/8 and so on. Hope u got it now.
 
GorgeousEyes

GorgeousEyes

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Iridescent said:
If the original value is 'x', in the first half-life the no. of counts remaining will be x/2. In the next half-life, it will be half of x/2 i.e., x/4. In the next half-life, it will be half of x/4 i.e., x/8 and so on. Hope u got it now.
Click to expand...
Yeaaah finally Got it , Thank youu .
 
M

mohammedalk

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guyz, as far as u know that both of the maths papers (paper 2 & 4) may 2013 mark scheme have been published by a teacher, have u seen the mark scheme of chemistry/physics/biology paper 3's mark scheme ??? im really worried guys please help!!!
 
Iridescent

Iridescent

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mohammedalk said:
guyz, as far as u know that both of the maths papers (paper 2 & 4) may 2013 mark scheme have been published by a teacher, have u seen the mark scheme of chemistry/physics/biology paper 3's mark scheme ??? im really worried guys please help!!!
Click to expand...

That is a solved paper, not any mark scheme. So far, no solved papers of any science subject have been posted on the forums for june 2013.
 
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