Question

how do furnace heating systems typically work?
ignition of fuel creates a pressure change inside the furnace, causing a piston to exhaust hot air into the building.
a bimetallic strip absorbs thermal energy from the air outside of the building, causing the transfer of thermal energy from fuel to the air inside the building.
energy in the fuels chemical bonds is converted to thermal energy, which is then transferred to the air inside the building.
thermal energy from outside of the building is transferred to the inside of the building using a liquid.

Explanation:

Furnace heating systems work by burning fuel (e.g., natural gas, oil). The chemical energy in the fuel's bonds is converted to thermal energy through combustion. This thermal energy is then transferred to the air inside the building (for forced - air furnaces) or to water (for hydronic furnaces).

• The first option is incorrect because ignition of fuel creates thermal energy, not just a pressure change that directly exhausts hot air (a piston is not a typical part of a standard furnace exhaust mechanism).
• The second option is incorrect. A bimetallic strip is often used in thermostats (a control device for the furnace) to measure temperature, not to transfer thermal energy from outside air. Furnaces use fuel, not outside - air thermal energy as the primary source.
• The fourth option is incorrect as furnaces generate thermal energy from fuel combustion, not transfer thermal energy from outside using a liquid (that's more like a heat - pump process in some cases, but not a typical furnace).

Answer:

Energy in the fuel's chemical bonds is converted to thermal energy, which is then transferred to the air inside the building.