# Just To Double Check

1. Jan 25, 2005

### altrez

Just two questions that are a small part of my ISU for physics. For this year we had to teach ourselves the unit on electricity and magnetism.

1. A bird stands on an electric tranmission line carrying 1200A. The line has a $1.0\times10^{-5} \Omega$ resistance per metre and the bird's feet are 30cm apart. What voltage does the bird feel.

2. What is the force per metre on a wirde carrying a 2.50A current when perpendicular to a 1.10T magenetic field.

For question one, I was first thinking that since the bird isn't grounded, it shouldn't really feel anything, but since the question probably wouldn't be as easy as that, i guess i'd have to calculate something.

Formula i used was just V=IR
$V = (1200 A)(1.0\times10^{-5} \Omega)(3.0\times10^{-1}m)= 3.6 \times 10^{-3} V$

That's what i got as a final answer

For question two, our books didn't really mention anything about formulas with the tesla unit so i guess we had to research it.

I found a formula that was :

$B=\frac {F} {IL} \vspace$

B is 1.10T
I is 2.50 A
L i think would be 1m since they wanted the force per metre.
F is the unkown

So in the end i got $F = BI = 1.10T \times 2.50A =2.75 N/m$

Just need some feedback on those questions.

Last edited: Jan 25, 2005
2. Jan 25, 2005

### vincentchan

good job :tongue:
i didn't check your number, but you have applied the formulas correctly