Calculating Current and Power in an Aluminium Wire: A Homework Guide

[KTTxx]

Homework Statement

You are working for the power company and wonder why we use a set voltage of power lines instead of a set current. You test your system on 38 m of aluminium wire with a diameter of 10.0 cm. The resistivity of aluminium is 2.65e-8 Ohm*meters. You place a 9000 Volt potential difference across the wire.
a. What is the current through the wire?
b. What is the power lost from the wire?[/B]

Homework Equations

The Attempt at a Solution

a. First, i need to find the Resistance of the wire by using equation R = pL /A
p = 2.65 e-8, L = 38 m, A= pi * (.05 m) ^2
Then i find the Current by I = V / R. I plug in the number, and i keep get the wrong answer.

For the power lost: Can i use the equation P = I * V ?[/B]

 

[gneill]

1. Homework Statement
You are working for the power company and wonder why we use a set voltage of power lines instead of a set current. You test your system on 38 m of aluminium wire with a diameter of 10.0 cm. The resistivity of aluminium is 2.65e-8 Ohm*meters. You place a 9000 Volt potential difference across the wire.
a. What is the current through the wire?
b. What is the power lost from the wire?

Homework Equations

The Attempt at a Solution

a. First, i need to find the Resistance of the wire by using equation R = pL /A
p = 2.65 e-8, L = 38 m, A= pi * (.05 m) ^2
Then i find the Current by I = V / R. I plug in the number, and i keep get the wrong answer.

What answers do you get for resistance and current?

For the power lost: Can i use the equation P = I * V ?[/B]

You can, yes. There are also two other forms of power equation that you can use: P = I²R and P = V²/R.

 

[KTTxx]

What answers do you get for resistance and current?

You can, yes. There are also two other forms of power equation that you can use: P = I²R and P = V²/R.

For the current, i get 70194473.39 A... , R = 1.23e(-4)

 

[gneill]

For the current, i get 70194473.39 A... , R = 1.23e(-4)

The values are good for the problem as stated, although you might want to use scientific notation for the current value and show only a reasonable number of significant figures.