What is the primary source of electrical power in the Cessna 172?

The primary source of electrical power in the Cessna 172 is the alternator. The alternator generates electricity while the engine is running, supplying power to the electrical systems and charging the battery simultaneously. This setup allows the aircraft to have a consistent and reliable power supply during flight, as the alternator maintains the electrical system's needs as long as the engine is operational.

In normal operation, the battery provides power primarily during engine start-up and when the engine is not running. While it is essential for the electrical system, it is not the primary source of power during flight. The generator is an older technology that is more commonly found in older aircraft and does not apply to the Cessna 172, which utilizes an alternator. Solar power is not a source of electrical generation in traditional Cessna 172 models, making it an unsuitable choice for this question. Thus, focusing on the alternator as the primary source highlights its crucial role in the functionality of the aircraft's electrical system.