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Preece's Law:
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Preece's law is an empirical formula used to calculate the fusing current of a wire, which is the current at which the wire will melt or fuse. It relates the fusing current to the wire diameter and a material-specific constant.
The calculator uses Preece's law equation:
Where:
Explanation: The equation shows that fusing current increases with the 3/2 power of the wire diameter, and is proportional to the material constant which accounts for the thermal and electrical properties of the material.
Details: Calculating fusing current is essential for electrical safety, fuse design, and determining the maximum current-carrying capacity of wires to prevent overheating and potential fire hazards.
Tips: Enter the material constant (k) and wire diameter in inches. Both values must be positive numbers. Common material constants: copper = 10244, aluminum = 7585, iron = 3300.
Q1: What is the material constant (k) for different metals?
A: The material constant varies by metal: copper ≈ 10244, aluminum ≈ 7585, iron ≈ 3300, silver ≈ 11300, gold ≈ 8900.
Q2: How accurate is Preece's law?
A: Preece's law provides a reasonable approximation for fusing currents but may not be precise for all materials and conditions. More sophisticated models exist for critical applications.
Q3: Does wire length affect fusing current?
A: Preece's law doesn't account for wire length. In practice, very long wires may have different fusing characteristics due to heat dissipation along the length.
Q4: What are the limitations of this equation?
A: The equation doesn't account for insulation, ambient temperature, airflow, or the specific alloy composition of the wire material.
Q5: Can this be used for fuse design?
A: Yes, Preece's law is commonly used as a starting point for fuse design, though actual fuse design may require additional safety factors and testing.