Why does a circuit need a complete path?
A simple steady-current circuit needs a conducting path from one battery terminal, through its components, and back to the other terminal.
Provide a potential difference
The battery maintains a voltage between its terminals. It supplies energy to charges moving through the external circuit.
Read the complete explanation +
Provide a potential difference
The battery maintains a voltage between its terminals. It supplies energy to charges moving through the external circuit.
Close the path
Closing the switch connects the conducting loop. Opening it interrupts steady current in this simple circuit.
Transfer energy
Current flows through the components. A resistor dissipates energy as heat; the lamp also emits light. Charge is not used up.
Complete the loop
The path returns to the battery. In a simple series circuit, the same steady current passes through each component.
About this visual model +
A battery, knife switch, resistor and bulb form one closed series loop. Follow the two battery terminals around the wire. Highlights identify the parts being explained; the switch stays closed.
A simplified DC circuit. Real components have resistance and heating; capacitors and changing fields require additional analysis.
- Battery: Maintains a potential difference by converting chemical energy into electrical energy.
- Switch: Opens or closes the conducting path.
- Resistor: Limits current and transfers electrical energy into heat.
- Lamp: Converts some electrical energy into light, and the rest into heat.
Further reading: Electric current ↗, Series circuits ↗