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Power Formula:
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The power formula P = I² × R calculates the power dissipated in an electrical resistance. This is known as Joule's first law, which states that the heat produced by an electrical current through a resistance is proportional to the square of the current and the resistance.
The calculator uses the power formula:
Where:
Explanation: The formula shows that power dissipation increases with the square of current, meaning small increases in current result in large increases in power dissipation.
Details: Calculating power dissipation is crucial for designing electrical circuits, selecting appropriate components, preventing overheating, and ensuring electrical safety.
Tips: Enter current in amperes and resistance in ohms. Both values must be positive numbers. The calculator will compute the power dissipation in watts.
Q1: Why is power proportional to the square of current?
A: This relationship comes from Joule's law, which states that the rate of heat production in a conductor is proportional to the square of the current and the resistance.
Q2: What are typical power ratings for resistors?
A: Common power ratings for resistors range from 0.125W (1/8W) to several watts, with higher power resistors used in applications with greater current flow.
Q3: What happens if a resistor exceeds its power rating?
A: If a resistor exceeds its power rating, it may overheat, change value, or fail completely, potentially causing circuit malfunction or damage.
Q4: Can this formula be used for AC circuits?
A: For AC circuits with purely resistive loads, the formula still applies using RMS values for current. For reactive loads, additional factors must be considered.
Q5: How does temperature affect resistance and power calculations?
A: For most materials, resistance increases with temperature, which means power dissipation may change as a component heats up during operation.