Originally Posted by thunderdax
OK I'll try to list possible options for each question:
1. A
2. D
3. B
4. unsure (although pretty sure its C or D)
5. C
6. B (although a wierd question cause resistance could come into it)
7. A or D
8. A or C
9. B or C
10. B or C
11. B
12. A (This is blackbody radiation, not the photoelectric effect)
13. A or C (Although im almost certain its C)
14. B
15. D
Now, for 7, ppl who answered D explain this. The coil rotates 90 degrees to the vertical. Take the bottom end. Using r.h.palm rule, this end has a force going to the left. But that is the same way it is being rotated. Since Lenz's law states the force needs to oppose the movement, how is it D?
And for 9, the copper ring on R is broken. How can there be circular currents going around it? I'm uncertain, but i still stand by C.
B.J said:
FOR QUESTION 7, turn the page 90 degrees and it will show the diagram like they normally show it. B and C are automatically ruled out because current doesnt flow like that. Using Right Hand Rule, D is the one that workd.
THey have forces go against eachother hence why they use split ring commutators so it doesnt stop at this angle of rotation
7 im willing to bet on is D
FOR QUESTION 9, Q has no currents thus falls straight down. R is split, it still has eddy currents because magnetic flux is changin around the metal. It just forms little circulating currents and has a little bit of resistance to falling. Q has maximum resistance because eddy currents are bigger and stronger there 9 is B. I had similar quesion in trial paper so im sure its B
ok, first of all for question 7 i reckon it's A, because first of all, you CAN'T use the right hand grip rule with the diagram they provide. now imagine the loop was spun 90degrees, so the wires were at the top and bottom. NOw use the right hand grip rule, and as the current remains in the same direction, you get A. (remember it's a convertional current the diagram's showing.), but then again, i'm only 65% sure.
for 8 i hope they cancel it :|, caz i thought it was a stupid AC and put d
for 9., i agree wif person on top, it's B, even thought the copper is not a "complete" circuit, but even a piece of metal would have eddy currents, and how is that a complete circuit? it's B, i'm 95% sure.
for 10 i can confirm it's B, look at the jacaranda text book, 100%
for 13. i'm 85% sure it's C, as the extra electron would mean it has more valence electrons, hence the gap from conduction band would be smaller than the valence band of the silicon.
Here's a revised set of solutions.
1. A
2. D
3. B
4. C or D
5. C
6. B (60%)
7. A or D
8. A or C
9. B
10. B
11. B
12. A
13. A or C (85% C)
14. B
15. D
damn i screwed that mc hard...