OCR Gateway Physics B - P4 P5 P6 - Unofficial Mark Scheme

Calculations of the top of my head

p5

Resultant velocity would be 6 so Y is greatest

Would take horse 7 seconds

Car wasn't over speed limmit, it was 6.5 m/s

P5 6 maker: 0.45

I think it was that when it gets dark the LDR gets a higher resistance and so has a higher share of the output voltage and when it gets really dark the LDR will have such a high resistance that the output voltage is basically the input voltage which is 5V - a logical 1 and so turns on the light



It was NOR

Resultant velocity was 6 for X not Y I think.

Posted from TSR Mobile

I put X too...
It was 3 in one direction and 3 in another, so is it correct to add the two opposite velocities?

I put X too...
It was 3 in one direction and 3 in another, so is it correct to add the two opposite velocities?

But it did not have that curvy shape of the OR gate...
So my answer for the six mark question is incorrect?

I thought it was subtract....

Posted from TSR Mobile

I thought it was an OR gate.

I realised after the exam. I did terribly.

Just thought that I'd make some predictions regarding the grade boundaries. Feel free to leave feedback.

Predicted grade boundaries P4 P5 P6 [HIGHER] 2016
The previous grade boundaries were as follows;
2015- A*: 54, A: 45, B: 36, C: 27
2014- A*: 57, A: 48, B: 39, C: 30
2013- A*: 52, A: 43, B: 34, C: 25
Personally, while the calculations were rather difficult and some of the questions were phrased oddly, the majority of the questions were accessible to a large group of people. My predictions for the grade boundaries are; A*: 55, A: 46, B: 36, C: 29.
Hope this helps!

I thought it was subtract....

Posted from TSR Mobile

The resistance in an LDR decreases as light intensifies and increases if light intensity decreases.
If resistor 1 has a higher resistance than resistor 2 (LDR), the voltage is taken through the first output. This means the security light will stay off.
If resistor 2 (LDR) has a higher resistance than resistor 1 the voltage will go through that and out the bottom output, powering the security light.
I'm not too sure if this is correct but it's what i put.

You do add dw. For resultant velocity you add and for resultant FORCE you subtract. The question clearly stated velocity.

Posted from TSR Mobile

The resistance in an LDR decreases as light intensifies and increases if light intensity decreases.
If resistor 1 has a higher resistance than resistor 2 (LDR), the voltage is taken through the first output. This means the security light will stay off.
If resistor 2 (LDR) has a higher resistance than resistor 1 the voltage will go through that and out the bottom output, powering the security light.
I'm not too sure if this is correct but it's what i put.

I'm sure you didn't! From the other science threads you seen really clever anyways

Posted from TSR Mobile

I did research and you are absolutely correct. Thanks for that, it's reassuring .

OCR Gateway Physics B
P4 P5 P6 + Section D
Unofficial Mark Scheme
Wednesday 22 June 2016

Module P4 - 25 marks
1) Radiation treatment
a) Explain why an alpha source cannot be used as a tracer [1]
(too ionising and so) will not penetrate out of the skin (1)

b)i) Explain why a radioactive source should not remain in the body for a long time [1]
to not cause damage to healthy living cells (1)

b)ii) What is the name given to how long a source stays radioactive? [1]
half-life / radioactivity (1) not sure [I believe I wrote half-life.]

c) Radiation may be used to treat brain cancer - explain why the head should be clamped [2]
so that the gamma rays are focused on the tumour (1)
to avoid damage to non-cancerous / healthy tissue / cells (1)

2) Fuses and wiring [6]
Marking points
why only two wires are needed: it is double insulated and so the earth wire is not needed - even if the live wire becomes loose, the plastic cannot become live: maybe include purpose of live and neutral wires (to carry the voltage and complete the circuit respectively)

why a fuse is needed: too large a current causes the fuse to melt, preventing flow of current, which prevents flex overheating and causing fire - and prevents further damage to appliance

why a 13A fuse is used instead of 3A: operating current must be between 3A and 13A so that the fuse does not break under normal operation (this would happen for a 3A fuse), but also breaks if the current gets too high

3) Static electricity
a) Complete the sentence [1]
he gains a positive charge because he loses electrons (1)

b) Explain how anti-static sprays work [1]
make surface of object conductive (1)

c) Explain why the small strip attached to his car may be unreliable [1]
not touching the ground / not made of a conductor (1) not sure [Because it was a small strip attached to the back of the car, I wrote something referring to the fact that it may be unsupported/weak/easy to break off.]

d) Describe and risk and benefit of the petrol filler [2]
risk: spark due to static charges which could cause an explosion (1)

benefit: quick to use as flows out quickly [This would be a benefit, as it reduces the time in which the pump and the car are in contact, thus reducing the risk of explosions.] / does not build up as much charge as it flows out quickly (1) not sure

4) Nuclear radiation
a) Write the letters in order [2]
B, E, F, A

four correct (2)
two or three correct (1)
otherwise (0)

b) Explain the purpose of boron rods but explain why they need to be removed some times [2]
absorb excess electrons to stop reaction going out of control (1)

(need to be removed so that) there are enough neutrons for the reaction to continue (1)

5) Power, current, resistance and voltage
a) Calculate the output voltage of the adapter [2]
94V (2)
incorrect answer with workings (1)

b) In which country will the iron have the highest electrical power? They all use the same current. Explain your answer [1]
Kenya, because it has the highest input voltage (1)

c) In Japan, the iron is bad at ironing out creases. She attaches a variable resistor and then it become better at ironing out creases. Explain why [2]
before, it had a low power as they all used the same current and it had the lowest input voltage (1)
variable resistor can be used to decrease resistance and increase current, making the power greater (1)

Your comment made me laugh and thank you. I'll just hope my examiner is half asleep so I get extra marks AND my exam is not remarked by someone else. And the probably of this happening is...well, let's not go there.