GCSE OCR 21st Century Triple Science (CBP1-7) Thread Watch

student97
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#1381
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#1381
well atleast turn out to be low since everyone finds it hard! 34/60 in physics last year for an A*!!!
OCR always expect stuff in the 6 markers that hardly relate to the question, so I think it's best if you go in to alot of detail, i do this is 3 markers as well, just to be safe!!
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lyricalvibe
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#1382
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(Original post by azo)
The rapid response bit implies it was a reflex, where the information isn't processed. So I don't think you talk about the CNS as the brain doesn't decide what to do, as it is involuntary. IDEK, you have an impressive memory to recall that question!



I just had a look at the spec and you are correct that relay neurons are in the CNS, so it isn't wrong but I don't think you talk about it co-coordinating a response or anything as
understand that this arrangement of neurons into a fixed pathway allows reflex responses to be automatic and so very rapid, since no processing of information is
required
Yeah I know, I said that I differentiated the 2 as separate areas, doing that is wrong, all a relay neuron is is a specialized part of the cns specific for reflexes and yes no information is processed. My point was simply that saying the cns was in a different place than the relay neuron is incorrect, the nervous impulse always takes the same pathway into the cns to the relay neuron as the spec says but in less detail. - But yes the question was talking about the reflex arc
Did you mention the synapse?
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Amyjonesx
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#1383
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#1383
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39 marks for an A* in june 2012
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olmyster911
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#1384
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Can anyone explain half life to me? :confused:
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monisj1
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#1385
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is it likely rutherford could come up tomorrow?
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Isabella~
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#1386
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How would you answer "Explain how an AC current is made as opposed to a DC current"?
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student97
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#1387
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(Original post by olmyster911)
Can anyone explain half life to me? :confused:
im sure someone else can help better, but basically:

the atom's nucleus is unstable and wants to get stable, so it emits radioactive rays (alpha, beta or gamma)randomly, however there is a pattern because more and more atoms are becoming stable and there are less unstable atoms left, so less radiation is emitted, so less activity. half life is the amount of time it takes for activity to reduce by half, or the time taken for half the sample to 'decay' (become stable.


"the time taken for half of a radioactive sample to decay/

time taken for activity to drop to ½" - one mark answer for JAN 2013 paper on halflife
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chocolae787879
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#1388
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#1388
ANyone have a link for the june 2013 paper and mark scheme?
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chocolae787879
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Ac/Dc is likey to come up because it hasnt come up at all i dont think
Also can someone explain how to do the Pc/Sv = Pc/Sc
And the questions where they ask like E=mc2 but with to the power of 10 ect
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azo
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#1390
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#1390
(Original post by lyricalvibe)
Did you mention the synapse?
No.. Should I have? :confused:
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-sophia-
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#1391
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Are motors likely to come up tomorrow? We haven't been taught them so should I learn about them now?
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Fyt
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#1392
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Can anyone link the June 2013 paper please.


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lyricalvibe
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#1393
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(Original post by azo)
No.. Should I have? :confused:
i didn't feel it neccesary in the exam but i've heard a couple people have :/ i'm thinking it wasn't neccesary and the question wanted more of the mechanics of a reflex than synapse but i couldn't think it a bad thingg :/
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Fyt
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(Original post by -sophia-)
Are motors likely to come up tomorrow? We haven't been taught them so should I learn about them now?
Learn about them just in case.


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TomSmith98
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#1395
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The rapid response bit implies it was a reflex, where the information isn't processed.
But surely the squirrel seeing the predator wouldn't cause it to automatically run away for example. The running motion of the legs cant be a reflex can it?...The squirrel must make a conscious decision after seeing the predator to run away otherwise it would not be able to control its legs. :confused:
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azo
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#1396
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(Original post by lyricalvibe)
i didn't feel it neccesary in the exam but i've heard a couple people have :/ i'm thinking it wasn't neccesary and the question wanted more of the mechanics of a reflex than synapse but i couldn't think it a bad thingg :/
I don't think it was needed, there was lots to write about anyway.

(Original post by TomSmith98)
But surely the squirrel seeing the predator wouldn't cause it to automatically run away for example. The running motion of the legs cant be a reflex can it?...The squirrel must make a conscious decision after seeing the predator to run away otherwise it would not be able to control its legs. :confused:
I get what you are saying but I think it can as the knee-jerk reflex is a reflex so is automatic, and so is the reflex for snails to retreat into their shells they don't think about it
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superdarklord
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#1397
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#1397
Hope this clears stuff up for you guys, happy to answer any further questions you have


(Original post by lyricalvibe)
Can someone clear this up please?I really don't know :confused:
If mains electricity is induces and it is AC, how is it transported to houses and such? Wouldn't the current just turn back and forth and never actually go anywhere as opposed to direct current which goes in one direction?
Ac doesn't mean that the current travels back and forth. Alternating current refers to the fact that the voltage is induced by rotating a magnet in a coil. As it rotates every half turn, the magnetic field changes and so as it rotates in one direction, the field constantly changes. This is what it means by alternating current.

The electricity still 'moves' in one direction through the wires this is stepped up using a transformer to a very high voltage so that less electricity is wasted as heat as it travels through the wires. When it comes to our houses, it is given to us at 230volts. This has been stepped down due to a step down transformer.

(Original post by ed__)
Can anyone please help me with all the motor stuff and induction stuff on p5? I don't understand it one bit and still have all of p4 and p6 to do I'm not at all screwed. You will be have the best karma ever and i will worship you for the rest of my life, please help!!!!
The way a generator works is using electromagnetic induction. A magnet is rotated in a coil of wire which changes the magnetic field after every half turn. This induces a voltage, and possibly a current (in a complete circuit). Due to the voltage changing and so the current reversing as the magnet rotates, this is called alternating current (AC)

A motor uses the idea that a current carrying wire will experience a force when placed in a magnetic field. Essentially, a motor converts electrical energy to kinetic energy.

1) a coil of current carrying wire is placed in a magnetic field
2) this experiences a force
3) the force causes one side of the coil to be pushed upwards and the other pushed downwards
4),the coil is on a spindle and due to this motion, the coil rotates
5) every half turn, the split ring commutator reverses the current to ensure the motor keeps spinning in one direction
6) an axle can now be attached to the motor, it will spin as a result. This can be attached to a fan, wheels on an electric car etc.

(Original post by olmyster911)
Can someone explain resistance to me please?

I thought it meant the current was reduced which meant less electricity (?) so that with an LDR the resistance would be highest in day so the light was off, but it is the opposite to this. Why?
In an LDR, resistance falls in daylight. LDRs are present in street lamps and make the light switch ON when it is dark outside.

In bright light, the resistance is very little. As a result, the current does not do work on the component (bulb). Energy isn't supplied to the bulb, the current does no work and so the light doesn't switch on.

In the night, resistance is higher. As the current travels through, the current is made to do more work on the component. It transfers more energy and so the light switches.


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Sulfur
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#1398
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(Original post by monisj1)
is it likely rutherford could come up tomorrow?
I think so, what could you say except:

Rutherford's experiment involved shooting alpha particles into a gold leaf
Some particles were repelled/scattered which showed that the nucleus was positive
This also shows that the nucleus holds most of the mass
Most particles were went straight through which showed that the atom was mostly empty space

(Original post by Isabella~)
How would you answer "Explain how an AC current is made as opposed to a DC current"?
Yup I need to know this as well! I know that:

AC is alternating current (/\/\/\/) - current changes direction
DC is direct current (-------) - current travels in a straight line
AC is used because it's easier to generate and distribute over long distances
DC is used in batteries
AC is used to transfer most of the electricity/used in houses and household appliances

(Original post by chocolae787879)
Ac/Dc is likey to come up because it hasnt come up at all i dont think
Also can someone explain how to do the Pc/Sv = Pc/Sc
And the questions where they ask like E=mc2 but with to the power of 10 ect
What would you say about AC/DC apart from what I've said (above)?

Vp - voltage in primary coil
Vs - voltage in secondary coil
Np - number of turns in primary coil
Ns - number of turns in secondary coil

In the exam, they'll give you three of these and tell you to calculate the missing one //OR// you may be told to use 230V (seeing as it's the household voltage from the national grid) if it doesn't give you three values then this is your best bet.

For example: Vp - 360, Vs - 24, Np - unknown, x Ns - 12
Vp/Vs = Np/Ns
360/24 = x/12
15 = x/12
x = 15 x 12 = 180

E = mc2 is the equation to calculate the energy released by nuclear fusion/fission
E is the energy, m is the mass and c is the speed of light
The speed of light is a constant at 3x10^5 km/s or 3x10^8 m/s - unless stated otherwise

Calculate the energy released when the mass is 15 kg and the speed of light in m/s
E = 15 x 3x10^8
E = 4,500,000,000
E = 4.5x10^9 m/s
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BarneyMartin
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#1399
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#1399
(Original post by ToLiveInADream)
I actually love those Vp/Vs turns on the transformer questions now..hope it comes up tomorrow
Can you explain it then please because I have no idea?!
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Sulfur
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#1400
(Original post by Fyt)
Can anyone link the June 2013 paper please.


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I posted it about 20-15 pages back.
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