Chapter 29, Problem 2P

You are working as an expert witness in a civil case. You have been hired by the attorney for a company that manufactures compasses. The company is being sued by a novice hiker who used one of the company’s top-level compasses. The hiker claims that the compass was defective, sending him off in a different direction from his desired direction. After taking off in the erroneous direction, he dropped and lost his compass so that he could not take subsequent measurements. As a result, he became lost for days, with the subsequent ill effects on his health and lost wages from missed days at work. The hiker has provided the exact location at which he took the erroneous compass reading. You take a trip to this location and look around. You notice that there is an electric power transmission line directly above sour location, running in a north–south direction. Using trigonometry, you determine that the power line is a vertical distance of 6.65 m above the ground. Upon returning to your office, you contact employees of the electric power company, who tell you that that particular rural power line actually carries DC current with a typical magnitude during the day of 135 A. (a) In order to provide advice in this case, you calculate the magnetic field caused by the power line at the location of the hiker. (b) What advice do you give to the attorney?