1. What is Power Across a Resistor?

Definition: This calculator computes the power dissipated by a resistor in an electrical circuit using the voltage across it and its resistance.

Purpose: It helps engineers, technicians, and students determine the power dissipation in resistors to ensure proper circuit design and component selection.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( P \) — Power dissipation (watts)
• \( V \) — Voltage across resistor (volts)
• \( R \) — Resistance (ohms)

Explanation: The voltage squared is divided by the resistance to calculate the power dissipated as heat by the resistor.

3. Importance of Power Calculation

Details: Proper power calculation ensures resistors are appropriately sized to handle the power dissipation without overheating or failing.

4. Using the Calculator

Tips: Enter the voltage across the resistor (in volts) and the resistance value (in ohms). Resistance must be greater than 0.

5. Frequently Asked Questions (FAQ)

Q1: What happens if power exceeds resistor rating?
A: The resistor may overheat, change value, or fail catastrophically. Always use resistors rated for at least 2x the calculated power.

Q2: Can I use this for AC circuits?
A: Yes, if using RMS voltage values. For peak voltages, additional calculations are needed.

Q3: Why does power increase with voltage squared?
A: Because both current (V/R) and voltage increase together, resulting in power (V×I) increasing quadratically with voltage.

Q4: What's a typical resistor power rating?
A: Common ratings are 1/8W, 1/4W, 1/2W, 1W, and up for power resistors.

Q5: How does temperature affect the calculation?
A: Resistance may change with temperature, affecting power dissipation. For precise calculations, consider temperature coefficients.