What is the Maximum Magnetic Field Under Overhead Power Lines?

[Angie K.]

Homework Statement

You want to get an idea of the magnitude of magnetic fields produced by overhead power lines. You estimate that the two wires run about 30 m above the ground and about 2.9 m apart. A call to the local power company provides the information that the lines operate at 10 kV (rms) and provide a maximum of 44 MW to the local area. Estimate the maximum magnetic field you might experience walking under these power lines.

Homework Equations

B=mu0*I/2 pi r

The Attempt at a Solution

Would I be able to find the current from the given power and voltage?

Power = V^2/I where V is the voltage (10kV) and I is the unknown current and power is 44 MW

Then using that to find the magnetic field

B=mu0*I/2 pi r

and I'm not sure which value for r to use? Would it be 2.9m/2 because it's the radius I'm interested in?

Thanks in advance!

 

[ehild]

Homework Statement

You want to get an idea of the magnitude of magnetic fields produced by overhead power lines. You estimate that the two wires run about 30 m above the ground and about 2.9 m apart. A call to the local power company provides the information that the lines operate at 10 kV (rms) and provide a maximum of 44 MW to the local area. Estimate the maximum magnetic field you might experience walking under these power lines.

Homework Equations

B=mu0*I/2 pi r

The Attempt at a Solution

Would I be able to find the current from the given power and voltage?

Power = V^2/I where V is the voltage (10kV) and I is the unknown current and power is 44 MW

The formula for the power is wrong.

Then using that to find the magnetic field

B=mu0*I/2 pi r

and I'm not sure which value for r to use? Would it be 2.9m/2 because it's the radius I'm interested in?

Thanks in advance!

You are interested in the magnetic field at your place, on the ground. How far are you from the power lines?

 

[rude man]

Remember you have 2 line with current traveling in opposite direction. There will need to be a vector superposition of the two lines' currents.