My Teacher Couldn't Answer This...

[Sharpend]

Dave, could of left her stewing a little longer, the punters in the bar think their walking across a desert! Dry house as bar maid last seen walking in the direction of her mobile!

 

[Andy™]

Almost. R1 = (R2 x Rt) / (R2-Rt) :coat

oops, had it written correct in front of me, and got it wrong when typing it in

 

[Andy™]

Current: 10A

Rt: 40ohm

R1: 45ohm

R2: 360ohm

Am I right? (This is gonna get embarrassing if I'm wrong again ).

thats what i got

 

[misssweden]

YES!

Thank you so much for all your help guys. <3

And thanks for the useful formula, I'll use that in the future. My tutor is gonna be well confused

 

[SPECIAL LOCATION]

A lot of these sort of college questions often tend to have nice easy numbers for the answers...

And the figures you are getting back for calcs @ 400v are quite nice values...

If you did it @ 230v you get some numbers that are a bit more messy!

So I would guess 400v is the right supply voltage.

I am just trying to guess what the missing part of the question was.....

perhaps it should have given the current through the 45ohm resistor as well??

:C

 

[misssweden]

Dave, could of left her stewing a little longer, the punters in the bar think their walking across a desert! Dry house as bar maid last seen walking in the direction of her mobile!

Hahaha! I'm actually off tonight . Have considered ways of combining bar work and homework. Shouldn't be impossible if I start a pint of Guinness and leave that to sort itself out, do another draught pint with my left hand and use my right hand for the calculator Takes a woman to perfect that level pf multi-tasking

 

[misssweden]

A lot of these sort of college questions often tend to have nice easy numbers for the answers...

And the figures you are getting back for calcs @ 400v are quite nice values...

If you did it @ 230v you get some numbers that are a bit more messy!

So I would guess 400v is the right supply voltage.

I am just trying to guess what the missing part of the question was.....

perhaps it should have given the current through the 45ohm resistor as well??

:C

Yes you're right. It does tend to be easy numbers. I haven't tried it on 230v yet though.

I would have liked it to have given either voltage or total current. Not sure I could work it out if I only knew the current and resistance in one resistor...?

 

[steptoe]

how Id love to be a fly on the wall when you are back in class and tell the lecturer that he needs to give you an answer before you can answer his question,! :slap

 

[misssweden]

Even better, would you like to cover for him if he goes on holiday? Now that could be an interesting lecture ;p

 

[SPECIAL LOCATION]

Yes you're right. It does tend to be easy numbers. I haven't tried it on 230v yet though.

I would have liked it to have given either voltage or total current. Not sure I could work it out if I only knew the current and resistance in one resistor...?

Resistors in series divide the voltage proportional to the resistor values...

Whereas resistors in parallel divide the current proportional to the resistor values....

So if the question had said "one resistor is 45ohms and has 8.888amps flowing through it"..

you could then carry on and calculate all of the other bits that you have just done....

as V=IR 45ohms x 8.888A = 399.96v {or 400v}

and...

from your earlier calcs your 360ohms would have 1.111A through it.

Total current 8.888 + 1.111 = 9.999 {10A}

360ohms : 45ohms is 8:1 ratio

1.111A : 8.888A is 1:8 ratio

 

[misssweden]

Ah yes you're right, sorry it's me that's getting confused If I have time tomorrow I'll do it on 230v and work out R1 and R2 as well.

 

[misssweden]

Finally managed to get hold of my teacher today to ask him how to solve this. Answer (surprise): "can't do it on top of my head, I'll get back to you tomorrow." Gaaah!

 

[ProDave]

Finally managed to get hold of my teacher today to ask him how to solve this. Answer (surprise): "can't do it on top of my head, I'll get back to you tomorrow." Gaaah!

He'll be googling the answer tonight and will find this thread.

 

[Andy™]

He'll be googling the answer tonight and will find this thread.

wonder if he will admit that tomorrow

 

[misssweden]

Haha that will be me failing Tech then

 

[Andy™]

Haha that will be me failing Tech then

why? its not as if anyone here gave you all the answers. we simply stated that you cannot answer the question with the information given, and guessed what one of the missing values may be, and you done the rest

 

[misssweden]

Well, I suppose that's true. I don't really see the point in asking for the answer, then I still won't know how to do it. Plus I'd probably be told to stick my homework somewhere where the sun doesn't shine

Anyway I saw him today and he said I should have picked a resistance for the second resistor (he suggested 45ohm like the other one) and done it that way. But he did admit that it was a stupid question and it couldn't be solved with the information provided.

 

[Sharpend]

That's education for you!!

 

[binky]

nice to know college hasn't changed much :slap

and also nice to see a young lady entering the trade :Applaud

 

[misssweden]

and also nice to see a young lady entering the trade :Applaud

That's if I manage not to barbeque myself before I'm qualified