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Fires start only in the presence of oxygen, fuel, and energy. There has to be enough energy provided, by either chemical, electrical, or physical means for the fuel to reach it's heat of combustion. For example, rubbing two sticks together generates heat energy by friction. If this heat energy is provided at such a rate that the fuel, wood, reaches it's heat of combustion then the wood will ignite, assuming the presence of oxygen. The reason you have to rub vigorously for wood is because the heat is dissipated in time so the energy is no longer localized.

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14y ago

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