What are negatively charged particles that dictate the direction of current flow?

The correct answer is electrons, as they are the negatively charged particles responsible for the flow of electrical current in a circuit. In electrical theory, current flow is defined as the movement of charges, and in most conductive materials, including metals, it is the electrons that are free to move and create an electric current. When a voltage is applied across a conductor, these electrons respond to the electric field and flow towards the positive terminal, thereby establishing a current. This movement of electrons constitutes the flow of electricity, which is a fundamental concept in understanding electrical circuits and systems.

In contrast, protons, while positively charged, are not free to move within conductive materials; they are typically found within atomic nuclei and do not contribute to current flow in circuits. Neutrons, as neutral particles within the nucleus of an atom, do not have any charge and therefore do not play a role in electrical conduction or current flow. Photons, being particles of light, do not carry electrical charge and are fundamentally different from charged particles like electrons in determining current behavior. Understanding the role of electrons in electric current is crucial for grasping electrical engineering concepts and circuit design.