What Is an Electrical Load?
A load is the component in a circuit that consumes or draws energy — a motor, lamp, resistor or speaker. It converts the power the source supplies into work. The load's resistance (or impedance) sets the current drawn from the source: a lower-resistance load draws more current. The source must be able to supply the voltage and current the load needs.
In electronics, a load is any component or device in a circuit that dissipates energy — that is, draws current from the source. A lamp, motor, resistor or phone — once connected to the circuit, all are loads.
The Concept of a Load
The source (battery, power supply) supplies energy; the load dissipates it. The current a load draws depends on the voltage across it and its resistance (Ohm's law: I = V / R).
Load Current and Power
The current a load draws is called the load current. The power the load dissipates is found with P = V × I. The more current a load draws, the more power it dissipates.
Types of Loads
| Type | Example | Behavior |
|---|---|---|
| Resistive | Resistor, heater, bulb | Current-voltage in phase |
| Inductive | Motor, relay, coil | Current lags voltage |
| Capacitive | Capacitor circuits | Current leads voltage |
The Source-Load Relationship
Every source can supply a limited maximum current. If the load tries to draw more than this limit, the source voltage drops or its protection kicks in. That's why a power supply is chosen with the load's total current in mind.
Common Mistakes
- Overloading the source: if the load's current exceeds the source's limit, the source heats up or shuts down.
- Forgetting inrush current: motor and capacitive loads can draw far more current than normal at the first instant.
- Being fooled by a no-load measurement: the no-load voltage can differ from the loaded voltage.
Frequently Asked Questions
What is a load?+
What sets the load current?+
What does “no load” mean?+
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