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Physics: Post your doubts here!

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1:
a constant non-zero value of E from 0 to 3 cm
a different constant non-zero value of E from 3 to 6 cm

E from 3–6 cm has the opposite sign to and larger value than E from 0–3 cm

Notes:

Emf is the rate of change of magnetic flux, which means it's essentially the gradient of the magnetic flux graph.
As the graph is straight (gradient is constant), the emf values will be constant.
Since the second part of the graph has a greater gradient and in the opposite direction, the emf will have a larger value and will have the opposite sign to the emf of the first part.
 
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2:
There are 3 parts of the current-time graph.

i) steadily increasing current until near t1, meaning that emf is constant (as emf is gradient of the graph, and the gradient is constant).

ii) sharp decline in current around t1. The emf for this region is much larger than in the first part as the gradient is much greater, and as the gradient is of opposite sign, the emf will have an opposite sign too.

iii) constant current. As current is not changing, there is no change in magnetic flux. Hence, there is no induced emf.

2DJpCmb.png
 
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3:

a) Binding energy is the energy required to separate the nucleons in a nucleus to infinity.

OR

Binding energy is the energy required to bring together nucleons in a nucleus from infinity. (first definition preferred)

b) ii)

Mass defect, ∆m = 211.70394 – 209.93722
= 1.76672u

binding energy = 1.76672 × 930

binding energy per nucleon = (1.76672 × 930)/210

= 7.82 MeV

Divide by 210 because there are 210 nucleons, and the questions asks for binding energy "per nucleon".

Hope this helps!
 
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Q. When a potential difference V is applied between the ends of a wire of a diameter d and lenght l, the current in the wire is I. What is the current when a potential difference of 2V is applied between the ends of a wire of the same material of diameter 2d and the lenght 2I?
SOMEONE PLS HELP WITH THIS Q!
 
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Q. When a potential difference V is applied between the ends of a wire of a diameter d and lenght l, the current in the wire is I. What is the current when a potential difference of 2V is applied between the ends of a wire of the same material of diameter 2d and the lenght 2I?
SOMEONE PLS HELP WITH THIS Q!

Resistance is proportional to length, and inversely proportional to diameter/radius squared.

Let the resistance of the first wire be R.

Resistance of second wire = 2*(1/4) R = 0.5R

Current = 2V/0.5R = 4I
 
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Resistance is proportional to length, and inversely proportional to diameter/radius squared.

Let the resistance of the first wire be R.

Resistance of second wire = 2*(1/4) R = 0.5R

Current = 2V/0.5R = 4I
THANYOUUU YOU MADE IT SO EASY! I was trying to solve it in twisted way
 
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This is paper 5 of 2015. I wanted to ask if the way of writing is okay ? Particularly if i should write in continuous prose or if points are fine
 

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This is paper 5 of 2015. I wanted to ask if the way of writing is okay ? Particularly if i should write in continuous prose or if points are fine
Hey there. I haven't read those points as I am sure you would have checked from marking scheme. Answering your question you can do whatever you want but I would strongly encourage you to write in paragraph format. I will tell you my personal experience about paper 5; I started it with writing in point format as that looked quick and easy method and as all the points if I cover in point format then no need of paragraph format, I use to get full marks in method but wasn't able to score in additional details. I thought lets try paragraph format may be that could help me. AND IT DID!!!!!!!!!!!!!!!!!! BINGO! In paragraph format there were many things that I could included which I was unable to add in point form, idk why, but the para foormat worked great with me I started getting 28 or 29 or 30 marks with that. So it all depends on you. If you can cover all points in point format then GO FOR THAT! but if u have problem like me try the way I did. xD

RIP my English. :p Ignore it. :D
 
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The question is 'describe the effect if any on the separation and on the maximum brightness of the fringes when the following changes are made.
The wavelength is increased by 1.5 factor keeping a and D constant
Effect on separation................. ....
Effect on maximum brightness of fringes ..
 
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Hi, can someone please explain how to do the graph for part c? this is mj 2016 paper 42
 

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