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

Amyjonesx
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#1321
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#1321
What are the normal grade boundaries for p456? Is it as high as chemistry and biology? For example is it still 40-45 for an A*? If it is i can wave my a* goodbye i am so bad at physics
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ed__
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#1322
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#1322
(Original post by Amyjonesx)
What are the normal grade boundaries for p456? Is it as high as chemistry and biology? For example is it still 40-45 for an A*? If it is i can wave my a* goodbye i am so bad at physics
no its nowhere near as high it was 31 for an a* last year so it can be only max 35 for a* this year
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tigergirl8282
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#1323
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#1323
Has anyone got the mark scheme for the June 2013 P456 paper? I'm kinda desperate as I couldn't find it on the website -_- Thanks

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cupcakes16
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#1324
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#1324
Is velocity just another word for speed?
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fannehh
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#1325
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#1325
can someone make a list of all the formlae for P4 please??
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Sulfur
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#1326
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#1326
(Original post by cupcakes16)
Is velocity just another word for speed?
Yup, but velocity has size and direction.
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Sulfur
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#1327
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#1327
(Original post by saeranee)
can someone make a list of all the formlae for P4 please??
It's all given in the exam.

The one's that aren't given as clearly are these though:

GPE = weight (kg) x gravity (ms2) x height (m)
Weight = mass (kg) x gravity (ms2)
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physicalgraffiti
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#1328
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#1328
(Original post by lyricalvibe)
Me to but physics scares me
It's just one of those subjects that's so interesting yet puzzling at the same time
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Amyjonesx
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#1329
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#1329
Has anyone got the p456 june exam???
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ganners28
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#1330
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(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!!!!

This is how I understand it!

Electromagnetic induction - When a magnet is moved in and out of a coil of wire, it induces a voltage the kines in the magnetic field are being cut. If the ends of the coil are connected (Making a circuit) it will induce a current. This is called electromagnetic induction.

Generators - As the magnet rotates, the voltage induced in the coil changes direction. As a result, this produces alternating current (A.C) and it changes direction every half turn of a magnet (An image/diagram might show this more clearly).

Transformers - When two coils of wire are close to each other other, alternating current will create a changing magnetic field in the iron core. Therefore, this will induce potential difference in the secondary coil of wire. Step up transformers increase voltage and decrease current to reduce energy lost as heat, in the cables. Whereas, a step down transformer does the opposite; reducing the voltage to mains electricity of 230v.

Motors - A motor is a coil of wire that rotates between opposite poles of a permanent magnet. A current carrying wire can exert a force on the magnet/ another wire, or it can experience a force if it is placed in a magnetic field. The lines of force must be at right angles to the direction of current and the magnetic field. If the current travels parallel to the magnetic field lines, it doesn't experience a force.

When current flows through the coil of wire, it will cut the field lines in opposite directions on each side of the coil; creating a pair of forces acting in different directions, causing the coil to rotate. A commutator is a rotary switch that turns with the coil. It's job is to ensure that as the coil rotates, the current direction into the coil is switched.

Motors are used in DVD players, kitchen appliances and electric motors (Vehicles).


I hope this kinda helped, and didn't just go straight over your head or confuse you more!
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fannehh
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#1331
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#1331
(Original post by Sulfur)
It's all given in the exam.

The one's that aren't given as clearly are these though:

GPE = weight (kg) x gravity (ms2) x height (m)
Weight = mass (kg) x gravity (ms2)
O really? I was getting really stressed because I thought we had to memorize them all! Thankyouu
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fannehh
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#1332
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#1332
Thought this might be kinda helpful for p4:
"You're in a car. driving down the road at a nice steady 60 miles per hour.

your velocity = 60 mph. your acceleration = 0 (since acceleration = change in speed / change in time and your speed doesn't change)

you're stopped at red light. your velocity = 0. your acceleration = 0 since your velocity equals a nice constant zero.

the light turns green. you step on the gas and your car speeds up. lets say from 0 mph to 60 mph in 5 seconds. your velocity changes from 0 to 60 mph. so your acceleration is 60mph-0mph over 5 seconds... ie 60/5 = 12 mph per second. notice the units? miles per hour per second. length per time per time.....length / time squared.

a police officer sees you speeding up at 12 mph / s a decides that's reckless driving. then pulls behind you and turns on his red lights. you slow down from 60 to 0 mph in say 20 seconds. your acceleration = velocity final - velocity initial per time = (0 - 60 )/ 20 s = -3 mph/s

when your stopped, your velocity = 0. so for the next 15 min you sitting in the back of the squad car and your velocity doesn't change. ie your acceleration = 0. "

( i didn't write this)
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olmyster911
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#1333
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#1333
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?
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Kitty260
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#1334
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#1334
p456 6 markers?
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Sulfur
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#1335
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#1335
(Original post by saeranee)
O really? I was getting really stressed because I thought we had to memorize them all! Thankyouu
These are what are given: http://www.ocr.org.uk/Images/144867-...igher-tier.pdf (page 2)
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Sulfur
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#1336
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#1336
(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?
I don't understand this also. I would've thought that the resistance would've been greater when light as there'd be more collisions through the heat, similarly with thermistors being hotter leading to more resistance and collisions, yet these are all the opposite?
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ganners28
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#1337
(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?
Resistance confuses me too!

I'm quoting this from my revision book...

The greater the resistance, the smaller the current will be. So, when you add resistors in series, the battery has to push charges through more resistors, so resistance increases and current decreases.

When you add resistors in parallel, there are more pathways for current to take, so the total resistance reduces and the total current increases.

N.B. When current flows, the moving charges collide with the vibrating ions in the wire, which gives them energy. Also, the increase in energy of a component causes it to heat up. Therefore, in an LDR as the light intensity increases, resistance is reduced and more current flows. Similarly in a thermistor, resistance will be low as temperature increases, and more current will also flow through the circuit.
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olmyster911
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#1338
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#1338
(Original post by ganners28)
Resistance confuses me too!

I'm quoting this from my revision book...

The greater the resistance, the smaller the current will be. So, when you add resistors in series, the battery has to push charges through more resistors, so resistance increases and current decreases.

When you add resistors in parallel, there are more pathways for current to take, so the total resistance reduces and the total current increases.

N.B. When current flows, the moving charges collide with the vibrating ions in the wire, which gives them energy. Also, the increase in energy of a component causes it to heat up. Therefore, in an LDR as the light intensity increases, resistance is reduced and more current flows. Similarly in a thermistor, resistance will be low as temperature increases, and more current will also flow through the circuit.
I thought you'd want more current to flow at night so the light turned on (???) I'm just really confused idek
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Amyjonesx
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#1339
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http://www.ocr.org.uk/Images/80706-r...accredited.pdf just thought id post a link to this past paper as not many people have done it, mark scheme is at the bottom
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ganners28
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(Original post by olmyster911)
I thought you'd want more current to flow at night so the light turned on (???) I'm just really confused idek
Yeah, that's right, I think! The more current, the more energy, the more light?
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