AQA A level Physics Paper 2 Unofficial Markscheme June 8

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bindz
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Post your answers here and i’ll edit

1.1) Calculate the maximum temperature rise over 1hr caused by the heater.
0.51k
1.2)
Higher pump speed means greater velocity of water, and so larger kinetic energy. 3/2KT=KE, so temperature of water rises



2.0) This displays two charges, one of charge Q and one of +46 nC, 120mm apart from each other.

2.1) Definition of electric field strength.
The force per unit of charge on a small positive test charge placed in the field at a distance R from the source of the field

2.2) At a point P that is 66mm right of charge Q, the electric field strength is 0, find the value of Q.

2.3) Must a net amount of work be done by bringing a charge to point P in the field from infinity?
I said yes, because at an infinite distance, E=0. Work must be done to bring charge from infinity , to in range of field

2.4) Displays a ball on a thread swinging and about to collide with a wall. Circular motion question.

Describe the motion of the ball if the string breaks.
Horizontal velocity vector is accelerated by field. Downwards acceleration of gravity; circular/parabolic trajectory

3.1) Describe what is meant by a capacitance of 370uF (x10^-6 micro)

3.2)
T = RC, 1 = R * 370uF,

So R must be 1/370x10^-6 = 2700 Ohms.

3.3)

3.4) Calculate the time for the charging current to drop by half.
0.69 seconds

3.5) For charging, calculate the time for the capacitor to reach 3.0mC

4.1) State Lenz's Law

4.3) How does the ammeter reading display the concept of Lenz's law?

4.4) A coil of 1 turn (length 32mm x 32mm even sides) in a uniform magnetic field (0.38T), was moved from inside the field to a point outside the field.

The maximum reading of emf induced was 2.9x10^-4, calculate the time taken in moving the coil outside the field.
1.34 sec

4.5) The coil is now rotated in the field and the maximum reading of voltage was 5.1mV, find the angular speed of the coil.
13.1rad/s
5.1) What is the most likely source of radiation used to sterilize medical equipment to be used.

A couple people said alpha cause of its ionising properties.
I said gamma due to no harmful by products from reaction

5.2) Why should we not be worried about the components becoming irradiated after this process?

short half life,
5.3) With aid of a calculation, explain why the results of detected activity of a source do not follow the inverse square law of radiation.

Distances: 0.2, 0.5, 1.0 and Activities: 9013, 1395 and 242 respectively


The constant of proportionality K was not constant in this so does not follow invrse sq. law.

5.4) Give two reasons why these results do not follow the inverse square law.

6.2) How could you model a decay of a substance with a greater number of nuclei?

Use greater vol of water

6.3) How could you model a decay with a smaller decay constant?

Use a smaller gap in the thin tube or tap to reduce flow

6.4) Calculate the half life of Rb in a sample. With a decay constant of 1.42x10^-11 years^-1

Sorry for missing information on the question here.

I got around 4.88x10^10 for this.

6.5) A sample of Rb has 1.23mg present now, much many grams were present 4.47x10^9 years ago?

I got around 1.07g for this but I will not post my method unless I find the answer to be right as it may be misleading (and foolish x-( )

6.6) Find the activity of the sample of 1.23mg of Rb


7.0) Nuclear decay

7.1) Draw a decay chain of two elements following an alpha, two beta minus(es), and an alpha decay.

Again a graphical question so not much help here x-(

7.2) There is an imbalance in the number of protons and neutrons in the nucleus of atoms.

Explain this imbalance using the fundamental forces experienced in the nucleus, and give ranges for which they are felt.

7.3) Show the decay of 205 - 82 Pb (Lead) by electron capture to 205 - 81 Tl (Thallium)
pb+e---->ti +gamma+electron neutrino

7.4) Tl is left in an excited state. Electromagnetic radiation is released from this decay process, state two sources of this radiation.

I said from the de-excitation of electrons releasing gamma photons, and not sure about the other but possibly infra-red from heat? (Perhaps this is also related to the excitation of electrons).

7.5) Why is 99 - 43 Tc (Technetium) safe to use in medical procedures
Short half life, insoluble in blood, gamma emmiter so weakly ionising


thanks to guccimane for these answers


SECTION A
1)0.5K temperature rise
2)
capacitor question)
resistance of resistor~2700 ohms
half life of current was 0.69 seconds
draw b=v0-v0e^-t/cr, asymptoting at 9.8V
Moon rock question) 1.3x10^-3 grams initally
Magneic field question) angular velocity of 13.1 rad/s

SECTION B
gradient of graph) 0.341(A)
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alvan15
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Did anyone get B for the first MC?
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MatthewEvans0105
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Temperature rise of around 0.51k
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AV_Luke
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Temp rise 0.51k

Resistance was liike 2707 Ohms becuase RC=1 so R=1/c.
Half life of current I said equals ln(2)RC so 0.69 s.
Time for charce to decay to 3mC I got 1.75s.

Got around 13.1 or 14 for the angular velocity.

4 marker on the forces inside the nucleus (and thier ranges) and neutron to proton imbalance. I worte about the repulsive elctrostatic force between protons over infinte distance and the strong force acting on all nucleons.
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math24601
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What was the gradient for the first multiple choice??
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ImiT
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(Original post by math24601)
What was the gradient for the first multiple choice??
I put D but have no idea, Its definitely not A
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BTAnonymous
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(Original post by math24601)
What was the gradient for the first multiple choice??
MC 8.0 100/293=0.341 (i think it was A)
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math24601
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(Original post by ImiT)
I put D but have no idea, Its definitely not A
I don’t think it was D (sorry) because to get 5 it would be 100/20 but the change in Y was only about 33
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Lewis233_
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That was aids
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Cat-ion
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(Original post by math24601)
What was the gradient for the first multiple choice??
Pretty sure I put A because converting Celsius to kelvin?
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Champ171299
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First multiple choice I got A. I think it was like 0.341
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math24601
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(Original post by Cat-ion)
Pretty sure I put A because converting Celsius to kelvin?
But it was a temperature change and 1K = 1C ??
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BTAnonymous
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(Original post by math24601)
But it was a temperature change and 1K = 1C ??
You had to extrapolate the line down to 0Pa which is -273 degrees celcius. So i think the initial temp was 20 degrees celcius so just 100/273+20
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Cat-ion
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(Original post by math24601)
But it was a temperature change and 1K = 1C ??
I think it was you had to work out the gradient and 100/293 or something
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bindz
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(Original post by AV_Luke)
Temp rise 0.51k

Resistance was liike 2707 Ohms becuase RC=1 so R=1/c.
Half life of current I said equals ln(2)RC so 0.69 s.
Time for charce to decay to 3mC I got 1.75s.

Got around 13.1 or 14 for the angular velocity.

4 marker on the forces inside the nucleus (and thier ranges) and neutron to proton imbalance. I worte about the repulsive elctrostatic force between protons over infinte distance and the strong force acting on all nucleons.
For the capacitor connecte with a 9.8V supply and a resistor in the circuit, what would the max voltage across the capacior be? Would it be 9.8V?
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BTAnonymous
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What did everyone put for the question with the nuclide apparatus with the water? I got 2cm because it had a half life of 19 seconds i think so 57 seconds is 3 half lives so 16/2^3.

I then said to increase the initial water level but wasn't so confident with that.

then i said to use a liquid with a lower density.
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Champ171299
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For the first multiple choice, I extended the line to the negative axis to get the x-intercept as -273°C. At that value, pressure was 0 so I used change in pressure as 100 and change in temperature as 293 (20—-273) and got 0.341 (A)
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CompSciNinja
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(Original post by BTAnonymous)
What did everyone put for the question with the nuclide apparatus with the water? I got 2cm because it had a half life of 19 seconds i think so 57 seconds is 3 half lives so 16/2^3.
Me too
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BTAnonymous
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(Original post by jaspreetb)
For the capacitor connecte with a 9.8V supply and a resistor in the circuit, what would the max voltage across the capacior be? Would it be 9.8V?
That's what threw me off. The voltage on the capacitor could never be 9.8V because the resistor 'uses' some of the emf provided by the cell.
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Claudo Z
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(Original post by AV_Luke)
Temp rise 0.51k

Resistance was liike 2707 Ohms becuase RC=1 so R=1/c.
Half life of current I said equals ln(2)RC so 0.69 s.
Time for charce to decay to 3mC I got 1.75s.

Got around 13.1 or 14 for the angular velocity.

4 marker on the forces inside the nucleus (and thier ranges) and neutron to proton imbalance. I worte about the repulsive elctrostatic force between protons over infinte distance and the strong force acting on all nucleons.
I got exactly the same
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