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What type of current does a typical gas furnace use for ignition?

  1. Direct current (DC)

  2. Alternating current (AC)

  3. Both AC and DC

  4. None of the above

The correct answer is: Alternating current (AC)

A typical gas furnace uses alternating current (AC) for ignition. This is because gas furnaces are designed to operate on the electrical supply commonly provided in households, which is AC power. The ignition system in gas furnaces often utilizes a transformer to step down the voltage, providing the necessary energy to create a spark for ignition. This process relies on AC power to function effectively, as it allows for the proper cycling of electrical components within the furnace. Direct current (DC) is not commonly used in gas furnace ignition systems, as these systems are configured to run on the AC voltage supplied from standard electrical outlets. Therefore, AC is the appropriate answer as it aligns with the design and operational standards of most residential gas furnaces.