Physics: Post your doubts here!

[Konstantino Nikolas]

I am facing lots of difficulties in electric field chapter.
I can never solve a full question.
Help required.

^^ His videos are pretty good ... helps you understand the concept.

Or these from Khan Academy

 

[The Sarcastic Retard]

^^ His videos are pretty good ... helps you understand the concept.

Or these from Khan Academy

I will get back after watching this video and again solving few questions.
Thanks.

 

[The Sarcastic Retard]

Hey

Could anyone please help me out with the following questions it would be of immense help:-
View attachment 59324

View attachment 59325
I have no idea why both are 3A :3

The b) part of the following is my doubt
View attachment 59326
View attachment 59327
View attachment 59329

View attachment 59328
In the ms for b part where did the 25J come from?


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.

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

 

[The Sarcastic Retard]

Hey

Could anyone please help me out with the following questions it would be of immense help:-
View attachment 59324

View attachment 59325
I have no idea why both are 3A :3

The b) part of the following is my doubt
View attachment 59326
View attachment 59327
View attachment 59329

View attachment 59328
In the ms for b part where did the 25J come from?


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.

last questions, its coz we are reversing.

 

[The Sarcastic Retard]

Hey

Could anyone please help me out with the following questions it would be of immense help:-
View attachment 59324

View attachment 59325
I have no idea why both are 3A :3

The b) part of the following is my doubt
View attachment 59326
View attachment 59327
View attachment 59329

View attachment 59328
In the ms for b part where did the 25J come from?


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.

http://physics-ref.blogspot.in/2015/04/physics-9702-doubts-help-page-114.html - Q580

 

[Charlotte20102013]

Hi can someone help me with this please:

An iron block of 30 kg mass and 90°C temperature is dropped into an insulated tank that
contains 50 kg of water at an unknown temperature. At the same time a paddle wheel is driven
by a 400 W motor is activated to stir the water. It is observed that thermal equilibrium is
reached after 20 minutes with a final temperature of 28°C.

Determine: a) The initial temperature of the water. b) The entropy generated by this process. Explain the significance of the entropy change obtained.

Your help will be greatly appreciated! Thanks!

 

[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)