1. Brake Pedal: When you press the brake pedal, it activates a switch (brake light switch).
2. Brake Light Switch: This switch is a simple electrical contact. When the brake pedal is pressed, it closes the circuit, completing the electrical path.
3. Wiring: The switch is connected to the car's electrical system via wiring. This wiring runs from the switch to the brake lights themselves.
4. Brake Lights: The brake lights are simply incandescent bulbs (older models) or LEDs (some later models) that illuminate when electricity flows through them. The current flows through the completed circuit created by pressing the brake pedal.
5. Power Source: The power source is the car's battery. The entire system relies on a functioning battery and alternator to provide power.
6. Fuse: A fuse protects the brake light circuit from overloads. If there's a short circuit, the fuse will blow, preventing damage to the wiring.
In short, pressing the brake pedal completes an electrical circuit, allowing electricity to flow from the battery, through the switch, the wiring, and finally to the brake lights, causing them to illuminate. If any part of this system fails (bulb, switch, wiring, fuse), the brake lights won't work.
