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Power Formula:
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Power in a resistor refers to the rate at which electrical energy is converted to heat energy. When current flows through a resistor, electrical power is dissipated as heat according to Joule's law of heating.
The calculator uses the power formula:
Where:
Explanation: This formula calculates the power dissipated by a resistor when the voltage across it and its resistance are known. The power is proportional to the square of the voltage and inversely proportional to the resistance.
Details: Calculating power dissipation is crucial for selecting appropriate resistor wattage ratings, preventing overheating, ensuring circuit reliability, and designing efficient electronic systems.
Tips: Enter voltage in volts and resistance in ohms. Both values must be positive numbers. The calculator will compute the power dissipation in watts.
Q1: What happens if power exceeds resistor rating?
A: If power dissipation exceeds the resistor's wattage rating, it can overheat, change value, or be permanently damaged, potentially causing circuit failure.
Q2: Are there other power formulas for resistors?
A: Yes, power can also be calculated using P = I² × R (current squared times resistance) or P = V × I (voltage times current).
Q3: What are common resistor power ratings?
A: Common ratings include ¼W, ½W, 1W, 2W, 5W, and higher. Surface mount resistors typically range from ⅛W to 1W.
Q4: How does temperature affect power calculation?
A: Resistance changes with temperature, which can affect power dissipation. For precise calculations, consider the resistor's temperature coefficient.
Q5: When should I use derating for power calculations?
A: Derate power ratings by 20-50% in high-temperature environments or for critical applications to ensure reliability and longevity.