The ____ theory states that current flow is produced when an electron from one atom knocks electrons of another atom out of orbit.

• A. Bump
• B. Collision
• C. Ionization
• D. Conduction

Answer: (A)

The idea being tested is how current can arise when collisions cause atoms to ionize. When a high-energy electron from one atom strikes another atom and has enough energy to eject one of its electrons, that atom becomes ionized and releases a free electron. Those free electrons (and the positively charged ions created) can then move under the influence of an electric field, producing current. This process is described by the ionization theory of current flow, often discussed in the context of gas discharge or plasmas, where ionization creates the charge carriers needed for conduction. Conduction in metals, by contrast, relies on electrons moving through a lattice without ejecting electrons from atoms, so it isn’t about ionization. The term bump theory isn’t a standard description of electrical current, so it doesn’t explain how current is carried.