Currents in dc transmission lines can be 100 A or higher. Some people are concerned that the electromagnetic fields from such lines near their homes could pose health dangers. For a line that has current 150 A and a height of 8.0 m above the ground, what magnetic field does the line produce at ground level? Express your answer in teslas and as a percentage of the earth's magnetic field, which is 0.50 G. Is this value cause for worry?

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To find the magnetic field produced by a long, straight current-carrying wire at a point, we use the formula for the magnetic field (B) at a distance (r) from the wire: \( B = \frac{\mu_0 I}{2\pi r} \), where \( \mu_0 \) is the permeability of free space (\( 4\pi \times 10^{-7} \) T·m/A), \( I \) is the current, and \( r \) is the distance from the wire.

Substitute the given values into the formula: \( I = 150 \) A and \( r = 8.0 \) m. This will allow you to calculate the magnetic field at ground level.

Convert the Earth's magnetic field from gauss to teslas for comparison. Recall that 1 G = \( 10^{-4} \) T, so 0.50 G = \( 0.50 \times 10^{-4} \) T.

Calculate the percentage of the magnetic field produced by the transmission line relative to the Earth's magnetic field using the formula: \( \text{Percentage} = \left( \frac{B_{\text{line}}}{B_{\text{earth}}} \right) \times 100 \% \).

Discuss whether the calculated magnetic field value is a cause for concern by comparing it to typical environmental magnetic field levels and health guidelines.

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주요 개념

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Biot-Savart Law

The Biot-Savart Law describes the magnetic field generated by a steady current. It states that the magnetic field at a point in space is proportional to the current and inversely proportional to the distance from the current. This law is essential for calculating the magnetic field produced by the transmission line at ground level.

Magnetic Field Units

Magnetic fields are measured in teslas (T), where 1 T = 10,000 gauss (G). Understanding these units is crucial for converting the calculated magnetic field into a percentage of the Earth's magnetic field, which is typically around 0.50 G. This conversion helps assess the relative strength of the field produced by the transmission line.

Health Effects of Electromagnetic Fields

Electromagnetic fields (EMFs) are often scrutinized for potential health risks. While high levels of EMFs can be harmful, the fields produced by typical transmission lines are generally considered safe. Evaluating the calculated magnetic field against known safety standards helps determine if the field poses any health concerns.