iGCSE EDEXCEL PHYSICS DISCUSSION 2012
Physics exam discussion - share revision tips in preparation for GCSE, A Level and other physics exams and discuss how they went afterwards.
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Re: iGCSE EDEXCEL PHYSICS DISCUSSION 2012Basically imagine the coil and on the N side of the magnet the current goes in and the S side the current goes out so the motor effect is produced and the coil comes to the vertical position. If the commutator did not have gaps in it then the coil would try to turn to the expected horizontal position in which current would now on the N side of the magnet go out and on the S side the current would go in. This would also produce a motor effect but in the opposite way to what we desire so the coil is not able to complete a turn but is stuck in the middle in its vertical position. BUT with the split ring, when the coil reaches the vertical position, the connection is broken so the momentum from the motor effect allows it to topple over into another horizontal position. This time the sides are also switched so technically the current should go out on the N side and in through the S side but because the commutator broke connection and now remakes it, it resets these positions so the current actually, again, goes in through the N side and out through the S side thus allowing the motor effect to happen in the direction we desire again; this process keeps happening and the motor keeps turning.(Original post by edex123)
How exactly does a commutator work in a D.C. motor? I know that it keeps the current flowing in the same direction, but how? Could someone explain to me how?
I hope this helped, it's a bit difficult to explain without diagrams
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Re: iGCSE EDEXCEL PHYSICS DISCUSSION 2012Momentum is a measure of how easily something can be brought to rest and the quicker something's momentum is 'lost' the larger the force exerted according to the equation: Force = Change in Momentum / Time. Crumple zones and air bags in cars are designed to increase the time it takes for the car to come to rest thus decreasing the force acting by increasing the time which allows a better chance of survival for passengers. The seatbelt has a similar purpose, without it passengers would smash into the next neat or the windscreen, stopping their momentum quickly and causing injury. With seatbelts, the momentum of the passengers is lost at the same rate as the car because the seatbelt anchors the passenger to the car body meaning that their momentum is lost over a longer period of time, exerting less force and bettering chances of survival. In addition seat belts stretch a little, further increasing the time taken for momentum to be stopped.Last edited by member963009; 22-05-2012 at 09:40. -
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Re: iGCSE EDEXCEL PHYSICS DISCUSSION 2012Sorry I didn't see your post until after i posted(Original post by rtrtrt)
So, the coil begins to move up. When it reaches 90 degrees vertical, using Fleming's left hand rule, we can work out that this end of the wire will try to carry on moving up (so not
allowing it to rotate by moving down (clockwise)). The carbon brushes are not in contact with the split ring commutator here - they are in contact with where it splits. Momentum takes the
wire past 90 degrees, allowing the carbon brushes to be in contact with the other half of the split-ring. To enable it to carry on rotating, the split rings switch the direction of the
current, and by doing this the direction of the force changes, allowing the wire to move down.
So the three stages are:
1. Wire moves up.
2. Wire reaches 90 degrees vertical.
3. Wire carries on past vertical due to momentum.
4. Commutator switches direction of current.
5. Wire carries on by moving on downwards, resulting in a continuous rotation.
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Re: iGCSE EDEXCEL PHYSICS DISCUSSION 2012THANK YOU!!! The papers really don't it's all about experiments -_- To everyone on here saying oh Physics is so easy blah blah blah 'Call me arrogant for calling it easy', yes I agree the concepts are VERY easy but the papers don't test any of that! That's the point no one is willing to accept that's why I'm worried for physics because these people who claim the papers are easy; obviously their physics knowledge is far superior than mine because they can 'evaluate conclusions' and 'improve plans'(Original post by IWantSomeMushu)
After doing some past papers, does anyone else feel that the Physics exams do not test our knowledge well enough?
I know I'm only doing the Double Award, but the exams are kinda predictable.
Watch me fail now
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Re: iGCSE EDEXCEL PHYSICS DISCUSSION 2012(Original post by sahajkaur)
THANK YOU!!! The papers really don't it's all about experiments -_- To everyone on here saying oh Physics is so easy blah blah blah 'Call me arrogant for calling it easy', yes I agree the concepts are VERY easy but the papers don't test any of that! That's the point no one is willing to accept that's why I'm worried for physics because these people who claim the papers are easy; obviously their physics knowledge is far superior than mine because they can 'evaluate conclusions' and 'improve plans'
Just study the mark schemes. That's what I'm doing
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Re: iGCSE EDEXCEL PHYSICS DISCUSSION 2012Yes, to A2(Original post by numpty1225)
anyone going to take physics for as level? Hopefully they'll actually test some knowledge instead of this crap
Last edited by member963009; 22-05-2012 at 11:26. -
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Re: iGCSE EDEXCEL PHYSICS DISCUSSION 2012edexcel set an average june paper, but the jan paper was impossible - just how science works qs. its difficult to learn stuff if u dont know what to learn - actual physics which is easy or stupid evaluate improve question which make no sense whatsoever.
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Re: iGCSE EDEXCEL PHYSICS DISCUSSION 2012Pre-U.(Original post by numpty1225)
anyone going to take physics for as level? -
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Re: iGCSE EDEXCEL PHYSICS DISCUSSION 2012http://www.xtremepapers.com/communit...h-maths.13760/
just scroll down to physics -
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Well I think Physics Igcse is the most sane exam. With such an attitude that most people have physics will be definitely meaningless. Actually in the real world no one expects you to recall stuff but to evaluate stuff. That's what the paper is testing as it clearly says in the edexcels website
This was posted from The Student Room's Android App on my Nexus OneLast edited by StUdEnTIGCSE; 22-05-2012 at 12:13. -
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Re: iGCSE EDEXCEL PHYSICS DISCUSSION 2012This is a very precise explanation.(Original post by rtrtrt)
1. Wire moves up.
2. Wire reaches 90 degrees vertical.
3. Wire carries on past vertical due to momentum.
4. Commutator switches direction of current.
5. Wire carries on by moving on downwards, resulting in a continuous rotation. I would just add that the coil moves up as a result of the force that acts on it due to the current through it and the magnetic field acting on it, thus creating a force as per Fleming's Left Hand Rule. When the current alternates, it moves in the opposite direction, so the direction of force alternates as well (as the magnetic field remains constant).
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Re: iGCSE EDEXCEL PHYSICS DISCUSSION 2012The june paper was much better at testing knowledge and understanding. Asking you to make an experiment to measaure angle of refraction in a glass block does not test my understanding of physics IMO, if that's what you think realphysics is then you're in for a surprise at A -level
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Well theoretical physics is damn easy at this stage(Original post by sahajkaur)
The june paper was much better at testing knowledge and understanding. Asking you to make an experiment to measaure angle of refraction in a glass block does not test my understanding of physics IMO, if that's what you think realphysics is then you're in for a surprise at A -level
This was posted from The Student Room's Android App on my Nexus One
I hope this helped, it's a bit difficult to explain without diagrams 
post marking scheme for physics from May 2006 to November 2010. I just finished the papers and i cant find the MS anywhere
