anomalousdecay
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Does it have something to do with back emf?The answer is what Fizzy said
Does it have something to do with back emf?The answer is what Fizzy said
I don't know...I can't remember. Like I said earlier I'm tired af atmDoes it have something t do with back emf?
Only if the motor is supplied from a constant voltage supply rather than a constant current. Something that the question did NOT specify!The answer is what Fizzy said
Hmm you seem to be in the know. I hope you're correct haha cause I put b.Only if the motor is supplied from a constant voltage supply rather than a constant current. Something that the question did NOT specify!
Same.Hmm you seem to be in the know. I hope you're correct haha cause I put b.
Maybe they'll realize that they stuffed up (ambiguous question) and mark both b and d as correct.Hmm you seem to be in the know. I hope you're correct haha cause I put b.
Hmm.. This issue has to be raised.Maybe they'll realize that they stuffed up (ambiguous question) and mark both b and d as correct.
If they were just testing that students knew that a radial field implies that torque doesn't vary with angular position then they might have expected a constant current assumption and hence "b'.
One the other hand they may have been trying to test if students understood that back EMF increases with motor speed, and hence expected the assumption of constant voltage and answer "d". If this was the case however they *really* should have specified constant voltage operation.
Maybe they'll realize that they stuffed up (ambiguous question) and mark both b and d as correct.
If they were just testing that students knew that a radial field implies that torque doesn't vary with angular position, then they might have expected a constant current assumption and hence answer "b'.
One the other hand they may have been trying to test if students understood that back EMF increases with motor speed, and hence expected the assumption of constant voltage and answer "d". If this was the case however they *really* should have specified constant voltage operation.
It says DC motor. DC simply means unidirectional current (or voltage), it makes no implication of whether either the voltage or current is constant.It says DIRECT CURRENT, so I think we are stuffed.
It has happened in the past, but it is very rare.Protest to BOS I say
How often are two answers awarded? I put b...
for Q12, the Meissner effect is caused due to BCS which is due to the crystal lattice structure, the Messiner effect excludes magnetic fields. However, for long answer versions of this question you usually have to say the forces balance to allow the magnet to levitate. (which is what the question is asking)Q12, (a) is most correct. Meissner effect doesn't have anything to do with crystal lattice structure or the balancing of any gravitational forces anyway i believe.
14 should be (b) small values of d create very large values of E, and large values of d create very small values of E (suggested by your explanation too)
15 is (a) (panda15 explained already)
+Q17 looks like about 4 wrong
I'm pretty sure that the question just wants the textbook answer, which would be a).for Q12, the Meissner effect is caused due to BCS which is due to the crystal lattice structure, the Messiner effect excludes magnetic fields. However, for long answer versions of this question you usually have to say the forces balance to allow the magnet to levitate. (which is what the question is asking)
We only look at motors which have a constant supply voltage, so whilst I wholeheartedly agree with both answers being correct (in REAL life), unfortunately, I would say that only D would be correct (in HSC life)
2011 Biology Paper.Protest to BOS I say
How often are two answers awarded? I put b...