Physics: Post your doubts here!

[OmarKhan99]

9702/s12/qp/23
Question 2 (c)

CAN SOMEONE PLEASE DRAW THE GRAPH AND UPLOAD A PICTURE OF IT?

 

[ashcull14]

PLEASE ANY

View attachment 59311 View attachment 59310
PLEASE HELP!!!!

ONEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEE

 

[Catherine_1]

Q646 http://physics-ref.blogspot.in/2015/05/physics-9702-doubts-help-page-128.html

Thank you so much for your help. I just have a slight doubt, till now I was just aware that for RMS value we take Irms=I0/sqrt 2 so could you please briefly describe the area method used to answer it?

 

[Catherine_1]

Hey,
Could anyone, please explain me why do we use two diodes, when operating a relay.
The explanation given above doesn't seem consistent to me, since even if there is one diode D1, it won't allow the unwanted current to go to the op amp so how exactly is diode D2 helping anyway?
Thank you.

 

[Konstantino Nikolas]

View attachment 59335
View attachment 59336


9702/s12/qp/23
Question 2 (c)

CAN SOMEONE PLEASE DRAW THE GRAPH AND UPLOAD A PICTURE OF IT?

 

[The Sarcastic Retard]

Thank you so much for your help. I just have a slight doubt, till now I was just aware that for RMS value we take Irms=I0/sqrt 2 so could you please briefly describe the area method used to answer it?

Physicist I have to same doubt.

 

[The Sarcastic Retard]

this is the case for any graph. i believe most teachers don't explain it this case. they only give the final result for a square graph. anyway, this is mostly maths.

I dont get how u did 3 * 0.5

 

[Catherine_1]

Yeah Physicist could please explain this question a little more elaborately please.

 

[nehaoscar]

Thank you so much for your help. I just have a slight doubt, till now I was just aware that for RMS value we take Irms=I0/sqrt 2 so could you please briefly describe the area method used to answer it?

the I0/root2 is applicable for a sinusoidal waveform
For a square wave rms is same as peak
The factors for other waveforms are also given for you to have a look at

 

[nehaoscar]

View attachment 59339
Hey,
Could anyone, please explain me why do we use two diodes, when operating a relay.
The explanation given above doesn't seem consistent to me, since even if there is one diode D1, it won't allow the unwanted current to go to the op amp so how exactly is diode D2 helping anyway?
Thank you.

When current is switched off , an emf is induced since theres a fall in the flux within the relay coil.
The emf can damage the op-amp
so D2 is used so that it can pass the current around the coil without damaging the op-amp

 

[nehaoscar]

The b) part of the following is my doubt

In the ms for b part where did the 25J come from?

25J is change in internal energy
as mentioned earlier the internal energy was 195J and now it's 120J

 

[nehaoscar]

Hey

In this my doubt is the 5 c ii part
View attachment 59330View attachment 59331
View attachment 59332

So for averaging why are we multiplying the flux linkage by 2?

Please help, if possible.

Current is reversed so flux linkage was +3 first and its now -3
So change in flux linkage is 3-(-3) = 6 ie 2*3 so it's multiplied by 2

 

[nehaoscar]

View attachment 59311 View attachment 59310
PLEASE HELP!!!!

part a

Half life is 2.6
At t=0 iron is 0
At t=2.6 Mg has decayed to half it's initial value so iron has gained this much
At t = 5.2 Mg has decayed to half it's value at t=2.6 so iron has gained half it's value at t=2.6
Since at 2.6hrs we have taken 2 boxes, half of it will be 1 box
continue for the half lives and join the points to get a curve

Part b
http://physics-ref.blogspot.in/2014/10/physics-9702-doubts-help-page-4.html

 

[holoholo]

http://papers.xtremepapers.com/CIE/...nd AS Level/Physics (9702)/9702_s13_qp_41.pdf
Q11 b(iii)

 

[Catherine_1]

the I0/root2 is applicable for a sinusoidal waveform
For a square wave rms is same as peak
The factors for other waveforms are also given for you to have a look at

I can't thank you enough, for answering all my questions But Thaaaaank youuuuuu, seriously.

Actually, in the relay part I am still a bit confused if you could help me out, it would amazing.
I have elaborated my doubt in conjunction with your explanation


Thanks, once again.

 

[holoholo]

http://papers.xtremepapers.com/CIE/...and AS Level/Physics (9702)/9702_s08_qp_4.pdf
Q6 a and b explanation please

 

[Annarophic]

Guys can anyone give me the basic concept of the newly added 'Band theory' in physics 2016 syllabus.

 

[The Sarcastic Retard]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_s08_qp_4.pdf
Q6 a and b explanation please

a) Magnetic field is always normal to Force and torque = force * perpendicular distance. So for maximum torque the plane of coil should be normal to MF so that its normal to force and gives maximum torque (Physicist correct me if m wrong as its my current topic going in school)

b) As I mentioned above T = F * perpendicular distance
2.1 x 10^-3 = F * (2.8 x 10^-2)

 

[Catherine_1]

it is the way to obtain the Irms. of course, Irms is still a current.

Yeah, thanks No I just thought if you could have elaborated the method. Anyway, thank you so much. You have an amazing site btw.

 

[The Sarcastic Retard]

the I0/root2 is applicable for a sinusoidal waveform
For a square wave rms is same as peak
The factors for other waveforms are also given for you to have a look at

From where did u get this?