When fuel is mixed with air and ignited by an electric spark from the ignition system, what occurs?

When fuel is mixed with air and ignited by an electric spark from the ignition system, what occurs?

• A. Combustion
• B. Detonation
• C. Condensation
• D. Freezing

Answer: (A)

Ignition of a fuel–air mix by a spark starts combustion, an exothermic chemical reaction between the fuel and the oxygen in the air. This reaction releases heat and forms new molecules, causing the gas to expand and push against the piston to do work. The flame front moves through the mixture at subsonic speeds, delivering controlled energy to power the engine. Detonation, by contrast, is a violent, nearly instantaneous explosion that creates a shock wave and much higher pressures, which is undesirable. Condensation and freezing are phase changes and don’t describe the burning process.

Ignition of a fuel–air mix by a spark starts combustion, an exothermic chemical reaction between the fuel and the oxygen in the air. This reaction releases heat and forms new molecules, causing the gas to expand and push against the piston to do work. The flame front moves through the mixture at subsonic speeds, delivering controlled energy to power the engine. Detonation, by contrast, is a violent, nearly instantaneous explosion that creates a shock wave and much higher pressures, which is undesirable. Condensation and freezing are phase changes and don’t describe the burning process.