For example, we have chemical energy in the form of fuels and can convert that chemical energy into electricity. How does that process work? How can we turn kinetic energy of wind mills to electricity? How does sunlight turn into heat energy? How come we can measure energy in Joules when there are so many forms of it?
In: Chemistry
One thing to think about is that we can’t really measure energy. We can only measure things related to it, such as electric current. Or the mass of a moving body, and it’s velocity.
Actually, we can’t *really* measure velocity either – but we can measure displacement and time, and we know how they connect mathematically to form the useful concept of velocity.
You mention heat energy. One way to measure heat energy is to measure the temperature increase in eg. a volume of gas the energy flows into. But on a microscopic level, temperature is related to the kinetic energy of the gas molecules, which brings us to mass, time and displacement again.
The energy in the form of radiation from the sun is related to the frequency of the electromagnetic wave, which is a function of time again.
What makes energy such an important concept in physics is that it’s conserved, it cannot be created or destroyed. And conservation laws are very powerful tools in doing physics. So maybe try to think of energy as a powerful concept rather than anything ”changing form”. I’ll admit however that Einstein’s famous mass-energy equivalence stretches this intuition quite a bit.
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