The formula to find power when current and voltage are known is: P = IE
Understanding Power, Current, and Voltage
To fully grasp this formula, let's break down the concepts:
- Power (P): Measured in watts (W), power represents the rate at which energy is transferred or used.
- Current (I): Measured in amperes (A), current is the flow of electrical charge.
- Voltage (E): Measured in volts (V), voltage is the electrical potential difference that drives the current. (Note: While the reference uses "E" for Voltage, "V" is also commonly used).
The Formula: P = IE
The formula P = IE (or P = IV, if voltage is represented by "V") directly relates these three quantities. It states that power is equal to the product of the current and the voltage.
Example:
If a circuit has a current of 2 amps (I = 2 A) and a voltage of 12 volts (E = 12 V), then the power is:
P = IE = 2 A * 12 V = 24 W
Other Power Formulas (Joule's Law)
While P = IE is the direct answer to your question, it's helpful to know other related power formulas, often attributed to Joule's Law (as mentioned in the reference):
- P = I2R: Power equals the square of the current multiplied by the resistance. This is useful when you know the current and resistance, but not the voltage.
- P = E2/R: Power equals the square of the voltage divided by the resistance. This is useful when you know the voltage and resistance, but not the current.
These formulas are derived from Ohm's Law (E = IR) and the fundamental power formula (P = IE). The reference also provides the following Ohm's Law equations: I=E/R and R=E/I
Summary Table of Power Formulas
| Formula | Variables Used | When to Use |
|---|---|---|
| P = IE | Current (I), Voltage (E) | When you know the current and the voltage |
| P = I2R | Current (I), Resistance (R) | When you know the current and the resistance |
| P = E2/R | Voltage (E), Resistance (R) | When you know the voltage and the resistance |
