OCR B Physics G495 June 19th 2014 Unit 5

Think about it. As the magnet initially falls through the coil. It is travelling in a direction where the flux lines passing through the coil increase (Positive rate of change of flux). But once it is past the mid point of the coil, the magnet falls down in a direction where the rate of change of flux is negative, hence you get positive and negative emf induced.

Can you help me with question 12 part c, where you explain why there is no change in force on balance?

Think about it. As the magnet initially falls through the coil. It is travelling in a direction where the flux lines passing through the coil increase (Positive rate of change of flux). But once it is past the mid point of the coil, the magnet falls down in a direction where the rate of change of flux is negative, hence you get positive and negative emf induced.

Can you help me with question 12 part c, where you explain why there is no change in force on balance?

Taken from some question and answers released by the Matthew Arnold School Physics Department (they're based).



I'm not a chemist, so ionic bonding doesn't mean much at all to me, but you will probably be told in the exam which of the atoms/ions is positive and which is negative. Anyway, we know that systems will always tend towards the lowest possible energy state; so the electrons will tend towards bonding with the positive ion.

Now, earlier in this particular question sheet they'd said that Magnesium replaced Lithium ions at random points in the structure, and that the defect sites have a raised energy level. Why do they have a raised energy level? It must be because the attractive force of Magnesium relative to the Lithium is lesser.



So this energy level means that relative to the Lithium, electrons around Magnesium are of a higher energy level. The lower state around magnesium is greater than the lower state around lithium.



The radiation gives some electrons the energy to jump up an energy level to the Magnesium's energy level. However, the magnesium energy level is not like the fluorine; it's at a trough. A technical term for this state is metastability. The electrons are at a trough in energy levels, but it is not the lowest point in the entire system. The only way for them to get to the real bottom is to get enough energy to climb up to the fluorine's energy level to be able to tumble back down to the lithium.

An analogy is standing at the edge of a cliff. When stood still on the edge, you are at a metastable energy level. You're at a low state which is stable, but the introduction of energy in the form of me giving you a push quickly pushes you up the potential hill. You're now a hundred metres above the ground; I've given you the energy to climb up that energy hill. Now you're going to fall to the true lowest possible energy state, now you're at the top of the energy hill.

The heating is the man pushing the electrons off the cliff; it's giving them enough energy to climb the energy hill and tumble down towards the lithium energy level, which is the lowest energy level.

I hope I didn't ramble too much. If I'm horribly wrong, somebody tell me.

Here are the resources I used:

http://matthew-arnold.tmp.synergy-learning.com/mod/resource/view.php?id=4436
http://matthew-arnold.tmp.synergy-learning.com/mod/resource/view.php?id=4437

Jan 2011; Question 10c..

I don't understand what it's asking? Could someone kindly help me out?

It wants you to estimate the density of a gold nucleus. Because density = mass/volume (so density is proportional to volume) the ratio of nuclear radius/atomic radius = density of gold nucleus/density of gold atom. They give you the density of gold and the ratio nuclear radius/atomic radius so from this you can calculate the density of a gold nucleus. The assumption you have to make is that all of the mass of a gold atom is in the nucleus. Hope this helps

Thank you very much! I think I understand!

Might want to read my answer again: I made a slight mistake but I've edited it now

Think about it. As the magnet initially falls through the coil. It is travelling in a direction where the flux lines passing through the coil increase (Positive rate of change of flux). But once it is past the mid point of the coil, the magnet falls down in a direction where the rate of change of flux is negative, hence you get positive and negative emf induced.

Can you help me with question 12 part c, where you explain why there is no change in force on balance?

Could anyone give me a good definition of cleaving?


Never got taught that at AS :/