What does spark ignition require to ignite fuel?

Spark ignition specifically requires an external source of heat to ignite the fuel-air mixture in the combustion chamber. This is achieved through a spark plug, which generates a spark that ignites the fuel. The spark provides the necessary energy to initiate combustion at lower temperatures and pressures than would typically be needed by other ignition methods, such as compression ignition.

Spark ignition engines operate on the principle that a spark will create a small area of high temperature that can spread to the rest of the fuel-air mixture. This is especially important in gasoline engines, where the mixture must be ignited at precisely the right moment in the cycle for efficient operation.

Other options do not accurately represent the ignition process in spark ignition systems. For example, compression heat is more relevant to diesel engines, which utilize the heat generated by compressing air to ignite fuel. Combustion chamber heat refers to heat generated during the combustion process itself, and passive heat from the environment would not provide sufficient energy to initiate combustion in a controlled manner.