Answer:
The warm exhaust from the natural gas heater
is the result of taking usable energy (in the
natural gas), using some of it, then releasing
the less usable form (exhaust). or you can write -> Electricity is a usable form of energy, but heat is not. Heat is simply dissipated to the surroundings as a result of temperature gradient. Thus, energy is transformed from usable to non-usable form.
The following substance must be an A. Compound.
Radio waves. A cell phone transmits its signal to the towers by <em>electromagnetic waves</em>.
The electromagnetic waves are in the <em>radiofrequency region</em> of the electromagnetic spectrum.
Most cell phones in North America use radiofrequencies between <em>700 MHz and 850 MHz</em> and between <em>1700 MHz and 2500 MHz</em>.
Explanation:
on earth it is very difficult to start nuclear fusion reactions that release more energy than in needed to start the reaction.