Question
A surveyor 100 m from a long straight 200-kV DC power line suspects that its magnetic field may equal that of the Earth and affect compass readings. (a) Calculate the current in the wire needed to create a $5.00 \times 10^{-5} \textrm{ T}$ field at this distance. (b) What is unreasonable about this result? (c) Which assumption or premise is responsible?
1. $25 \textrm{ kA}$
2. This would result in a power loss of $3.4 \textrm{ GW}$ in copper transmission lines with a diameter of 2 cm and a length of 100km. This power loss is completely uneconomical.
3. The distance of 100 m is too far from the power line.
Solution Video