Question

Why must you stand closer to a small fire to experience the same warmth you get when standing farther away from a large fire?

Answer 1

You must stand closer to a small fire to experience the same warmth as from a large fire because a large fire radiates more heat due to its greater surface area, and the intensity of the heat reduces with the square of the distance due to the inverse-square law.

Step-by-step explanation:

The warmth you feel from a fire is due to heat transfer primarily through infrared radiation. A small fire requires you to be closer to experience the same warmth as standing farther from a large fire because the heat is dispersed over a larger area as you move away from the source. According to the concept known as the inverse-square law, the intensity of radiation is inversely proportional to the square of the distance from the source. This means if you stand twice as far from a heat source, you will experience only one-fourth of the heat.

Additionally, a large fire has a greater surface area from which heat can radiate compared to a small fire. If you increase the surface area, as when kindling is used to start a fire, more heat is radiated due to the increased area available for the emission of radiation, which is proportional to the fourth power of the absolute temperature and the surface area. Therefore, to feel the same level of warmth from a smaller fire, one needs to compensate for the lower surface area and reduced radiative power by being closer to the fire.

Answer 2

You must stand closer to a small fire to experience the same warmth you get when standing farther away from a large fire because of the amount of thermal energy that the large fire has transferred is more than the smaller one. A large fire provides a great thermal energy from the reaction. A small fire provides a less thermal energy from the reaction