Electric Current - What Am I Doing Wrong?

[evilempire]

By modeling the arm and the chest to be a cylindrical tube with a total length 2.0 m, cross-sectional area 10 cm^2, and resistivity 1.5 ohm*m, you can calculate the current in amperes through the person when a potential difference of 110 V is applied across the two hands. Assume that the current flows only through the modeled cylindrical tube. What is the current flow through the body?

The equation for resisitivity is R=rho*(L/A), and the equation for current is I=V/R. So for the R equation I plugged in the numbers, changing cm to .1 m, and got 30 ohms. I then divided 110 volts by 30 and got 3.7 (rounded to two sig figs), and my answer is not being taken as correct. The computer feedback system is saying 'check your units'. What have I done wrong?

Thanks.

 

[evilempire]

One idea I had - is the proper answer done such that I=V/((rho*L)/A), which would make I equal to 367 A?

 

[vincentchan]

the cross section area is in cm... and the rest of your problem is in SI ...

 

[evilempire]

the cross section area is in cm... and the rest of your problem is in SI ...

Yeah, so I converted it to m, 10 cm = .1 m.

 

[vincentchan]

and do you still got 367... if you do... change battery for your calculator, or do the calculation by hand...

 

[evilempire]

and do you still got 367... if you do... change battery for your calculator, or do the calculation by hand...

So it's not 367 or 3.67? Hmm...

 

[vincentchan]

it is 3.67

 

[evilempire]

it is 3.67

That's what I calculated initially, but the computer program won't take it, which led me to believe there was error in my calculation. Thanks for the help, I greatly appreciate it. I'm not sure what I'm going to do about answering the problem, but it's nice to know I had it right to begin with.

 

[vincentchan]

maybe you have to enter 3.67A... since the computer said check your unit

 

[evilempire]

maybe you have to enter 3.67A... since the computer said check your unit

It says 'A' outside the text box to the right, so I'm pretty sure they just want a value.

 

[vincentchan]

10 cm^2 = .o1 m^2...did you do the convertion correctly?

 

[evilempire]

10 cm^2 = .o1 m^2...did you do the convertion correctly?

It does? I thought 1 cm was .01 m, so 10 cm would be .1 m.

 

[vincentchan]

but 10 cm^2 = 10 (.01 m) ^2 = 10 * .001 m^2 = .01 m^2