Power Dissipation Calculator
Calculate power dissipated by resistors in series and parallel circuits using Joule's law P = I²R. Free online power dissipation calculator with per-resistor breakdowns and interactive charts.
About This Calculator
The Power Dissipation Calculator helps you determine how much electrical power is converted into heat by resistors in both series and parallel circuits. Whether you are an electronics hobbyist, engineering student, or professional circuit designer, this tool provides instant calculations of power dissipation using Joule's law of heating.
The calculator uses three fundamental formulas from Ohm's law and Joule heating: P = I²R (using current and resistance), P = V²/R (using voltage and resistance), and P = VI (using voltage and current). For series circuits, the same current flows through all resistors, so the highest-value resistor dissipates the most power. For parallel circuits, the voltage is identical across all branches, so the lowest-value resistor dissipates the most power. The calculator shows the equivalent resistance, total current, and a per-resistor breakdown table with voltage, current, and power values.
Power dissipation is a critical concept in electrical engineering because resistors have maximum power ratings. Exceeding these ratings can cause overheating and failure. Use this calculator to verify that your circuit design stays within safe limits for each component.
Frequently Asked Questions
What is power dissipation in resistors?
Power dissipation is the process where electrical energy is converted into heat as current flows through a resistor. According to Joule's law, the power dissipated by a resistor is P = I²R, where I is the current in amperes and R is the resistance in ohms. You can also use P = V²/R or P = VI depending on which quantities you know.
How do I calculate power dissipation in a series circuit?
In a series circuit, first add all resistances to find the equivalent resistance: Req = R1 + R2 + ... + Rn. Then calculate the total current using Ohm's law: I = V / Req. The power dissipated by each resistor is P_i = I² × R_i, and the total power is P_total = I² × Req.
How do I calculate power dissipation in a parallel circuit?
In a parallel circuit, first calculate the equivalent resistance: 1/Req = 1/R1 + 1/R2 + ... + 1/Rn. The voltage across each resistor equals the supply voltage V. The power dissipated by each resistor is P_i = V² / R_i, and the total power is P_total = V² / Req. The current through each resistor is I_i = V / R_i.
Which resistor dissipates more power in a series circuit?
In a series circuit, the resistor with the highest resistance dissipates the most power. This is because the same current flows through all resistors, and power is proportional to resistance (P = I²R). For example, with a 2 Ω and a 6 Ω resistor in series, the 6 Ω resistor dissipates three times more power.
Which resistor dissipates more power in a parallel circuit?
In a parallel circuit, the resistor with the lowest resistance dissipates the most power. Since the voltage is the same across all branches, power is inversely proportional to resistance (P = V²/R). A 2 Ω resistor in parallel dissipates more power than a 6 Ω resistor.
Does a series or parallel circuit dissipate more total power?
A parallel circuit dissipates more total power than a series circuit for the same set of resistors and supply voltage. This is because the equivalent resistance of a parallel circuit is lower, resulting in higher total current. Since power P = V²/R, a lower equivalent resistance leads to greater total power dissipation.
What is the maximum power a resistor can dissipate?
Every resistor has a power rating specified by its manufacturer, typically given in watts. This is the maximum amount of power the resistor can safely dissipate as heat without being damaged. Common ratings include 1/8 W, 1/4 W, 1/2 W, 1 W, and higher. Exceeding this rating can cause the resistor to overheat and fail.