# taht 2 tube question? (1 Viewer)

#### Libbster

##### Member
yeah i got 221 amps as well! yay for me lol

#### Spoz

##### New Member
Sounds like quite a few people used centimeters rather than meters for the distance...

Were you supposed to halve the current? Since the force is only acting on one of the wires rather than both, isnt the current needed half of 220...?

Even if I messed that bit up, I found this one of the easier questions to be honest because it was mathematical rather than 'assess the contribution to scientific thinking...'

Dumsum said:
by rama_v said:
Yep I got 221 amps, I did the calculation twice because I thouight hang on, this is extremely high considering its from a battery lol
But it seems thats the correct answer.
Just goes to show a battery would never actually cause the tube to jump
Bullshit. Most modern car batteries can supply more than 1kA when cold, although its not great for them. Since the parameters needed a high current to move the tube, a car battery was a good choice to supply it.

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#### boasboy

##### MUSTARD*
omagawd i think i might have got this right

#### ifsonotso_100

##### Meh
well i got 2000 something as well, for the next bit i said that this is a problem as power losses are tremendous, had no idea

#### Dumsum

##### has a large Member;
Spoz said:
Bullshit. Most modern car batteries can supply more than 1kA when cold, although its not great for them.
Well you learn something new every day eh... I thought the most these could supply was 50-60 A. Oh well.

#### Bokky

##### Member
what formula r u guys talking about there with the 223amps.

There was 40 seconds left in the exam and i left that question out so i just wrote out the I = 1/d^2 1 over distance squared, therefore I = 1/(0.1)^2
and got 100amps, meh at least i tried.

#### Anna K

##### New Member
Oh gosh I just realised I did the whole KI1I2l/d>mg, but instead of saying I1I2=I1^2, I said I1I2 = 2I1. Smart.

#### rama_v

##### Active Member
Spoz said:
Sounds like quite a few people used centimeters rather than meters for the distance...
Nah, the length of the wire was 1 metre and the separtion was 10 cm (0.1m)...when u plug inthose u get 221 Amps. I dont think you halve the current because its a repulsive force.

Also lol never knew about that car battery delivering kiloamps - guess i dunno much about cars

#### spank_meh

##### add me on MSN NOW!!!!
i didnt even do this q

#### haboozin

##### Do you uhh.. Yahoo?
i hope people didnt write "amps" in their exam paper...
thats not accepted... u either just do A or amperes.
It'd be silly to lose a mark for something like that

i wrote amps
like same shit

#### Spoz

##### New Member
rama_v said:
Nah, the length of the wire was 1 metre and the separtion was 10 cm (0.1m)...when u plug inthose u get 221 Amps.
Yes, I was referring to the people who got 2000A and 200,000A.

Does anyone know if you were actually supposed to halve the 220A since it was only one tube? Physics was my last exam and my brain has purged itself of all school-related knowledge.

#### Dumsum

##### has a large Member;
Spoz said:
Yes, I was referring to the people who got 2000A and 200,000A.

Does anyone know if you were actually supposed to halve the 220A since it was only one tube? Physics was my last exam and my brain has purged itself of all school-related knowledge.
Current is the same through both tubes, remember it's essentially a measure of electrons/second, and the same electrons that flow through the first tube are going to flow through the second tube (essentially).

#### Bizarre

##### Kicking Uni's bum.
I got 221.3A, I think. Something in that order of magnitude.

Amps is a perfectly acceptable way of writing Amperes. If you want to be really picky, you could say that Amperes in incorrect and you should write Cs^-1.

And the current was constant the whole way because it's a series circuit. Preliminary Physics - I1 = I2 = I3 for a series circuit.