M&g Q. (1 Viewer)

[ND]

I was doing a trial and came across this question (in reference to an induction motor):

"Explain why the motor produces a low power and is therefore unsuitable for use in heavy machinery"

I wasn't sure about this, and i don't have the solutions for the trial. This is what i answered:

Because the AC source (which the electromagnets are connected to) is 50Hz, that is also the frequency of the rotating magnetic field. 50Hz does not create a very fast magnetic field, and so the rotor does not rotate very fast, rending it unsuitable for many industrial uses.

Is this correct? i dunno...

 

[ND]

I've got another q. from the same trial:

At a theme park, a quickly falling vehicle relies ona magnetic field acting on a metal fin to slow it down. Explain how the magnetic field slows down the descending vehicle describing in detail the path of teh subatomic particles.

Ok i can explain this in relation to eddy currents being induced, but subatomic particles? wtf?

 

[Jumbo Cactuar]

well excel says that because AC is 50Hz that the induction motor is limited to only 3000rpm ,... but wouldn't power also involve torque? rpm is only limited speed...

 

[Jumbo Cactuar]

subatomic particles?! wtf? errr...

maybe that has something to do with an option as well cause I know that that question is too wack (excel mentions nothing in relation to subatomic particles!)

 

[Rahul]

aargh! i have done that trial paper...it is so shit! 60% of it is on M&G....wtf!?!?!?!

Originally posted by ND
"Explain why the motor produces a low power and is therefore unsuitable for use in heavy machinery"

I wasn't sure about this, and i don't have the solutions for the trial. This is what i answered:

Because the AC source (which the electromagnets are connected to) is 50Hz, that is also the frequency of the rotating magnetic field. 50Hz does not create a very fast magnetic field, and so the rotor does not rotate very fast, rending it unsuitable for many industrial uses.

Is this correct? i dunno...

yep thats right. you basicalyl need to talk about:
-the limitations of the power that can be produced.
-heavy machineries usually utilise large amounts of power.

you had that pretty much covered.

Originally posted by ND
I've got another q. from the same trial:

At a theme park, a quickly falling vehicle relies ona magnetic field acting on a metal fin to slow it down. Explain how the magnetic field slows down the descending vehicle describing in detail the path of teh subatomic particles.

Ok i can explain this in relation to eddy currents being induced, but subatomic particles? wtf?

thats just bullshit.....dont worry about understandign that...its either old syllabus or again the fucked up-ness of the exam. just talk about eddy currents and lez's law.....

hmm....ND, have you done q19. i think they may have made a mistake in that.

 

[ND]

Originally posted by Rahul

hmm....ND, have you done q19. i think they may have made a mistake in that.

Nah i just didn't do any calculation questions, who needs to practice those...

What mistake is it? Do you have the solutions?

Thanks for the replies guys.

 

[MyLuv]

Originally posted by ND
I've got another q. from the same trial:

At a theme park, a quickly falling vehicle relies ona magnetic field acting on a metal fin to slow it down. Explain how the magnetic field slows down the descending vehicle describing in detail the path of teh subatomic particles.

Ok i can explain this in relation to eddy currents being induced, but subatomic particles? wtf?

I think we can talk about electron moving in 1 direction in a magnetic field will experience a force resist to its motion(use a diagram)...Any1 got the answer for this ???

 

[Rahul]

Originally posted by ND
Nah i just didn't do any calculation questions, who needs to practice those...

What mistake is it? Do you have the solutions?

Thanks for the replies guys.

i do have the "solution", but they are
-1 mark for calculating radius.
-2 marks for defingin the field

they dont actually give any answers, stupid test.

hahah with that question if you work it out, the satellite ends up being buried in the ground!!!! hahahahaha
good one idiots.

the mistake i think may be that the satellite is 35 000m and not 35 000km

edit: i really dont think people should get worried about that exam. it was pathetic....i mean you only need to see their diagrams.

 

[ND]

Originally posted by Rahul

hahah with that question if you work it out, the satellite ends up being buried in the ground!!!! hahahahaha
good one idiots.

Hahah, i don't think i'll bother with their '02 paper...

 

[Rahul]

Originally posted by ND
Hahah, i don't think i'll bother with their '02 paper...

lol you shouldnt
you can do some of the easy questions for 'fun'