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A2 Physics | Post your doubts here

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brother u are correct ....emf in primary coil and emf in secondary are 180 degree out of phase........the question asked about current and emf in secondary coil which is ov corass 90 degree out of phase

Yea but whats the concept behind it? aren't primary current and primary emf in phase?
 
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on question (1ci) why do we use mass of the earth to calculate? when it asks to calculate gravitational potential of the object? Please explain!
 

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No i mean mean voltage. I heard its always zero in sinsoidal wave but how??

To find mean voltage, you need the sum of all the voltage under the sinusoidal graph, which is composed of peaks and valleys. Now if you add the areas under the (+) peak and the area above the (-) valley, the sum is zero. Through Mean=Sum of X/No. of X , whatever the number of X may be, the mean is zero is the sum of X is zero. So the mean voltage in AC is zero unless you remove the effect of direction by squaring.
 
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on question (1ci) why do we use mass of the earth to calculate? when it asks to calculate gravitational potential of the object? Please explain!

that means you haven't got the concept yet.
gravitational potential is work done in bringing unit mass from infinity to the point, meaning that you are not considering the mass that you are moving.
Besides, the mass of object is NOT given.. so no choice but to use mass of earth.

just remember the situation it works for all question
 
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well k i used pTIMES DELTA V......and got the anser......bt oe doubt...as we knw internal energy of ideal gas is 3/2 PV,,.....why it cnt be used here.....cnt undrstnd why it gives the rong ansa'
http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Physics (9702)/9702_w09_qp_42.pdf and i cnt understand why ms says insufficient info for answering the question relating to temp. change cos......we can use 3/2 pv to anser this
Why are you complicating the problem.
Work done is P x Delta V.
If it asks for change in K.e then you can use 3/2 Pv = 3/2 (NkT)
 
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-got anything about our Am bandwidth confusion?
-do we include the sign of the charges while calculating electric potential?
- I posted the image from a book, did you see that ? Apart frm that i did not get anything else

-No, we dont
 
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MARKING SCHEME SAYS :for gravitational, work got out as masses come together
/mass moves from infinity
for electric, work done on charges if same sign, work got out if opposite sign as charges
come together
what on earth does work got out mean?
 
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does a dc voltage vary in magnitude? because it has a max value and r.m.s value?
No, it does not vary

It has no r.m.s value
R.m.s value is the feature of a.c current
R.m.s value of a.c current is the value equaivalent to the d.c current value which produces the same power dissipation in a resistor
 
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MARKING SCHEME SAYS :for gravitational, work got out as masses come together
/mass moves from infinity
for electric, work done on charges if same sign, work got out if opposite sign as charges
come together
what on earth does work got out mean?
It means work is done by the masses
 
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for example j10 41 Q6 , it says dc voltage of peak value of 9 Volts, this means it has an r.m.s value?
in that case u know, a varying output will be produced...

rectification-jpg.9241

like the last one - the orange part...

so peak value is given ;)
 
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1) ideal gas compressed, means work done on it i.e increases, and they come closer together
Constant temperature means Internal energy is constant, so q must decrease.
2)heating of solid ---> thermal energy input / no expansion no work done.
3)melting of ice, thermal energy required to break bonds, no change in volume against atmosphere/ very small.
No, it does not vary

It has no r.m.s value
R.m.s value is the feature of a.c current
R.m.s value of a.c current is the value equaivalent to the d.c current value which produces the same power dissipation in a resistor
R.m.s value for ac current and for ac voltage, is therre a difference in definition.
Is it better to say equivalent to d.c current or do we say it is a steady constant value for current.
 
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