[Alexok]

I have a feeling principles of detection/analysing detections and maybe transformers will come up

[Alexok]

(Original post by Estelle123)
whats an electron neutrino?! infact wth is a neutrino?!

All need to know is that a neutrino has no charge. Anythig with a *blablabla neutrino* has no charge so will not show a path in a bubble chamber etc

[dzone25]

I am NOT having a good time right now... Can't seem to do anything without making a stupid mistake

Really hope transformers come up because they're easy but what else is likely? I need to focus my revision a bit its not going too well... Any tips?

Edit: I missed a bunch of lessons about electric field and all that sort of topics... Any notes would be appreciated as its hard to get my head round like Jan 2012 Q12

[d_94]

(Original post by dzone25)
I am NOT having a good time right now... Can't seem to do anything without making a stupid mistake

Really hope transformers come up because they're easy but what else is likely? I need to focus my revision a bit its not going too well... Any tips?

Edit: I missed a bunch of lessons about electric field and all that sort of topics... Any notes would be appreciated as its hard to get my head round like Jan 2012 Q12

Principles of detection/ analysing detections, transformers, circular motion

[astaraeal]

(Original post by dzone25)
I am NOT having a good time right now... Can't seem to do anything without making a stupid mistake

Really hope transformers come up because they're easy but what else is likely? I need to focus my revision a bit its not going too well... Any tips?

Edit: I missed a bunch of lessons about electric field and all that sort of topics... Any notes would be appreciated as its hard to get my head round like Jan 2012 Q12

Jan 2012 Q12 is about the production of magnetic fields by electric charges - a stationary electric charge produces an electric field, a moving electric charge produces a magnetic field.
If you have two objects both producing magnetic fields and their magnetic fields interact, the objects will either attract or repel each other.
For this question, the two wires have currents travelling in the same direction, so you can work out the direction of the magnetic field using the right hand rule (point your thumb in the direction of the current and your fingers curve in the direction of the magnetic field). If you get a friend and both of you place your right hands next to each other, you can see that your fingers point in opposite directions in between your hands - so the wires attract as the magnetic fields between them are in opposite directions, and each wire is in the magnetic field produced by the other wire.
You can also look at this from the point of view that there is a current-carrying wire in a magnetic field, so by Fleming's LHR, it experiences a force towards the source.
Finally, because there are two magnetic fields, there will be a neutral point between the wires where the fields cancel

[dzone25]

(Original post by d_94)
Principles of detection/ analysing detections, transformers, circular motion

But didn't detection come up in Jan 2012?

(I'm seriously hoping alpha particle scattering comes up again xD free marks)

Transformers are well easy enough just one formula? Circular motion isn't TOO hard considering I have to do M3

What gets me is the longer questions, I know what to write but sometimes they give marks for the most stupid things (like current in a wire produces a magnetic field ... Well duh?)

[astaraeal]

(Original post by dzone25)
But didn't detection come up in Jan 2012?

(I'm seriously hoping alpha particle scattering comes up again xD free marks)

Transformers are well easy enough just one formula? Circular motion isn't TOO hard considering I have to do M3

What gets me is the longer questions, I know what to write but sometimes they give marks for the most stupid things (like current in a wire produces a magnetic field ... Well duh?)

They tend to try and cover as many specification points as possible, so alpha particle scattering could show up *crosses fingers*

And I tend to state the obvious stuff first and then elaborate - it's not a perfect strategy though!

[naveeshan]

(Original post by whooshpaddy)
Most important to know momentum in more than one dimension, circular motion, electric fields, magnetic fields, emf, motors and transformers, particle acceleration and detection.

I predict questions on transformers, momentum in 3d and circular motion.

What does momentum in 3D exactly mean...Do you mean resolving the velocities in one direction and then using momentum conservation?

[EllaBella<3]

I would be really grateful if somebody could just confirm something for me!

With capacitance, as the capacitor charges, the voltage across it increases until it reaches the terminal voltage? Is this correct? Is this why the current decreases?

Also, i've got a question that says "as the coil rotates faster the current in it reduces" Explain this observation. Is this because as it rotates faster, flux is cut at a greater rate therefore the emf and voltage increases therefore the current decreases?

I hate electricity .. :L

[Karisliana]

(Original post by naveeshan)
What does momentum in 3D exactly mean...Do you mean resolving the velocities in one direction and then using momentum conservation?

Yes, can anyone post a worked example please as I find them really difficult

[astaraeal]

(Original post by EllaBella<3)
I would be really grateful if somebody could just confirm something for me!

With capacitance, as the capacitor charges, the voltage across it increases until it reaches the terminal voltage? Is this correct? Is this why the current decreases?

Also, i've got a question that says "as the coil rotates faster the current in it reduces" Explain this observation. Is this because as it rotates faster, flux is cut at a greater rate therefore the emf and voltage increases therefore the current decreases?

I hate electricity .. :L

See my post on the previous page for an explanation of the back emf in a motor

As for capacitance, the potential difference across a capacitor increases as it charges because there is a flow of electrons around the circuit from one plate to the other, so as the difference in charge builds up, so too does the potential difference.
This means that the potential difference across the resistor falls, as in a series circuit, total pd is shared between components, so V=V(capacitor) + V(resistor) and increasing V(capacitor) decreases V(resistor). As V=IR, and the resistor has constant resistance, decreasing V decreases the current. When V(capacitor) = total circuit V, V(resistor) = 0 so I = 0.

[Estelle123]

can anyone explain to me q5 multiple choice june 2011 about the car on the hump-back bridge? you had to say what the force is on the car from the bridge when the car is at the top of the bridge. (the answer is mg-mv^2/r)

[astaraeal]

(Original post by Estelle123)
can anyone explain to me q5 multiple choice june 2011 about the car on the hump-back bridge? you had to say what the force is on the car from the bridge when the car is at the top of the bridge. (the answer is mg-mv^2/r)

If you look at the forces acting on the car, there must be a resultant centripetal force acting on it at the top of the bridge to keep it moving in a circle, so the resultant force acting on it is mv^2/r. The two forces acting on it are its weight, mg, and the normal reaction from the bridge, R.
This gives mg-R = mv^2/r (the resultant force is down towards the centre of the circle so mg > R.)
Rearranging, R = mg - mv^2/r as required

[naveeshan]

(Original post by EllaBella<3)
I would be really grateful if somebody could just confirm something for me!

With capacitance, as the capacitor charges, the voltage across it increases until it reaches the terminal voltage? Is this correct? Is this why the current decreases?

Also, i've got a question that says "as the coil rotates faster the current in it reduces" Explain this observation. Is this because as it rotates faster, flux is cut at a greater rate therefore the emf and voltage increases therefore the current decreases?

I hate electricity .. :L

As the capacitor charges the voltage across it increases and the voltage across the resistor decreases.Since the resistance is a constant and according to V=IR the current decreases.

As the coil rotates faster there is a rate of change of magnetic flux linkage according to Faradays law.But according to Lenzs law the induced emf opposes the change causing it and in this case the change causing it is current and thus it decreases.

Hope it helps you

[EllaBella<3]

Do we need to know the charges on quarks?

[astaraeal]

(Original post by EllaBella<3)
Do we need to know the charges on quarks?

Only on the up quark (+2/3e) and the down quark (-1/3e). Anything else should be given

[EllaBella<3]

(Original post by astaraeal)
Only on the up quark (+2/3e) and the down quark (-1/3e). Anything else should be given

Thank you - I saw a question and it didn't give it to you, I was having a panic that I was going to have to learn a bunch of numbers .. less than 24hrs before the exam! :L

[astaraeal]

(Original post by EllaBella<3)
Thank you - I saw a question and it didn't give it to you, I was having a panic that I was going to have to learn a bunch of numbers .. less than 24hrs before the exam! :L

It's not too hard to remember - the top, charm and up quarks are all + 2/3e, and the down, strange and bottom are all -1/3e

Was the question an exam question?

[King_Arthur]

I.ve attached a Revision notes set i found online was very useful
but it has Unit 4 and Unit 5

[Bourii]

Momentum in 2D btw peeps, not sure why people are talking about resolving vectors in 3D.