Definition
Voltage
The electromotive force from a power source that pushes electrons through a circuit, often described as electric pressure. Measured in volts (V)
Definition
Current
The flow of electric charge through a circuit, caused by the movement of electrically charged particles, such as electrons. Measured in amperes (A)
Definition
Resistance
The opposition to the flow of electrons in an electrical circuit. It can be calculated using Ohm’s Law, which relates resistance (R), voltage (V), and current (I): R=V/I. Measured in ohms (Ω)
Definition
Power
The rate at which electrical energy is transferred or used in a circuit, measured in watts (W). It depends on both voltage and current.
Electrical Calculations
- Designers must understand the relationships between voltage, current, resistance, and power in order to specify components and troubleshoot circuits.
- The key equations come from Ohm’s Law and Power Law.
Key Equations
| Equation | Meaning | Units |
|---|---|---|
| $V = I × R$ | Voltage = Current × Resistance | V (volts), A (amps), Ω (ohms) |
| $P = V × I$ | Power = Voltage × Current | W (watts), V (volts), A (amps) |
Rearranging Formulas
To find any variable, rearrange the formula:
- $I = \frac{V}{R}$ → Current = Voltage ÷ Resistance
- $R = \frac{V}{I}$ → Resistance = Voltage ÷ Current
- $V = \frac{P}{I}$ → Voltage = Power ÷ Current
- $I = \frac{P}{V}$ → Current = Power ÷ Voltage
