June 2011 G485-Fields, Particles and Frontiers of Physics

I think some people here are confusing this with OCR Physics B..
Comet? That doesn't come up surely...

time base - 50x10-6 s cm-1, pulse width - 2.4cm, ultrasound speed - 1.5 kms-1

- Work out the time difference between receiving pulse from the front of the head, and the back of the head first:

2.4 x 50x10-6 s cm-1 = 1.2 x 10-4 s

- Work out the difference in distance the echo has had to travel:

distance = speed x time; 1.5 x 10^3 x 1.2 x 10-4 = 0.18m

- Because this is the distance covered by the echo going to the back and then coming to the front again it's half this distance:

0.18/2 = 0.09m

For some reason I don't actually understand why its 2d....but I'll just memorise it. -_-

Solutions to follow once the paper is done?

Solutions to follow once the paper is done?

Those are always fun.
Seeing answers to the questions you thought you got right, are actually wrong.
Well, I guess it's okay when there's a moment of hope/happiness when everybody else plus you gets 3)c)iii) right.
However, I don't think it's much of a pay off when later on you are the only one to get 9)b)xvi) wrong.

In the end, I ALWAYS look anyway.

doubt it - only possible if someone miraciously remembers all of his/her answers - maybe if someone has access to the paper after the exam can post the solutions.

doubt it - only possible if someone miraciously remembers all of his/her answers - maybe if someone has access to the paper after the exam can post the solutions.

Oh, the ones in the book? I know. They're ridiculous. But look at the dates, they're so old. In class we had to do ones older than us.

You know the ones that are so old the photocopier prints them diagonally across the page somehow?

I find if I write down the questions and answers of the ones I get wrong and memorize them, it will help me with some of the weirdo questions they like to throw into our exam.

Was getting confused about Lenz's law... as simple as it may be to learn.. it talks about the conservation of energy is applied therefore the emf induced is the opposite of the change that caused it... as energy was put in to move it against the resistance force?

Im guessing the resistance force is the force that the induced current will experience which is upward if you are moving the wired downward through the mag field ... so its kinda like a drag effect, as it only is in effect when motion of the wire is in effect.

Someone set me straight please

I remember one hand is for induced current, EMI
I forgot what the other hand is for...

Direction of magnetic field around wire, Right hand rule with thumb?

There's more than that...
I remember saying Force with the left thumb and then Motion with the right thumb but I don't remember why

[INDENT]The bottom line is that Fleming's left hand rule is used for electric motors, while Fleming's right hand rule is used for electric generators.[/INDENT]

This is what I was looking for!

Left hand is for when it is already there,
Right hand is for induced.

this has been bugging me for a while...can you elaborate on what this resistive force is and how energy is conserved