You want to get an idea of the magnitude of magnetic fields...

Name: Problem 91, Chapter 20: Physics: Principles with Applications
Uploaded: 2019-09-19T02:14:33-08:00
Duration: 1 min 36 s
Channel: Farhanul Hasan
Description: You want to get an idea of the magnitude of magnetic fields produced by overhead power lines. You estimate that a transmission wire is about 13 m above the ground. The local power company tells you that the lines operate at 240 kV and provide a maximum power of 46MW. Estimate the magnetic field you might experience walking under one such power line, and compare to the Earth's field.

You want to get an idea of the magnitude of magnetic fields produced by overhead power lines. You estimate that a transmission wire is about 13 m above the ground. The local power company tells you that the lines operate at 240 kV and provide a maximum power of 46MW. Estimate the magnetic field you might experience walking under one such power line, and compare to the Earth's field.

Key Concepts

Comparison with the Earth's Magnetic Field

The Earth's magnetic field serves as a useful reference point, as its magnitude is relatively well known and consistent (typically tens of microteslas). Comparing a man-made magnetic field to that of the Earth helps in contextualizing its strength and assessing any potential effects or hazards.

Distance Dependence of the Magnetic Field

The magnetic field created by a current-carrying conductor decreases with increasing distance from the conductor. Understanding this spatial attenuation is key for estimating the magnetic field strength at specific distances, such as the field experienced by an observer at ground level beneath an overhead power line.

Biot-Savart Law

The Biot-Savart Law provides a mathematical description of the magnetic field produced by a small element of current. It is fundamental in electromagnetism for calculating the contributions of various segments of a current-carrying conductor to the overall magnetic field at a point in space.

Magnetic Field around a Current-Carrying Conductor

When an electric current flows through a conductor, it creates a magnetic field in the surrounding space. The strength and orientation of this field can be determined using fundamental electromagnetic principles, such as Ampère’s Law, which relates the current through the conductor to the magnetic field formed around it.

Calculation of Current from Power and Voltage

In electrical systems, power, voltage, and current are interrelated. The current in a system can be estimated by using the relationship between power and voltage, often expressed as power equals voltage times current. This calculation is crucial when determining the magnitude of the magnetic field produced by the current in the conductor.

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