Does the light bulb violate the conservation of energy law?
You put in 100 Watts of electric energy; you get out 100 Watts total of light and heat energy. With incandescents, you get maybe 10 Watts of light and 90 Watts of heat. Of course, the light is converted to more heat within nanoseconds, so ultimately you get 100 Watts of heat. If you are heating your home with ordinary thermostatic electric heaters, every Watt of lighting will take a Watt of average load off of your heater. So the 90 Watts is not wasted in Winter, and the light is essentially free, regardless of which type of bulb you use. In the summer, that 90 Watts requires you to run the air conditioner longer, so even more energy is wasted by incandescent bulbs.
Let’s look at an example of an electric light bulb. A light bulb changes electrical energy into light energy. If we were to measure these energies for one second, we might get energy numbers that look something like this: Electrical Energy In 100 J (joules) Equal to Light Energy Out 70 J (joules) This would suggest that energy is not conserved? Where did the other 30 J of energy go? Remember that energy can change into more than one form simultaneously. And if you feel a light bulb it is very hot. The “missing” energy must have gone into heat energy. So, the actual energies were more like this: Electrical Energy In 100 J (joules) Equal to Light Energy Out 70 J (joules) + Heat Energy Out 30 J (joules) This propensity for energy to change into more than one type of energy is extremely common. And the most common energy for this “missing” energy to go to is heat energy. Since our goal for the light bulb is for all of the electrical energy to go into light energy, the heat energy is really
let me straight this one, as you said “The conservation of energy law: Energy may change from one form to another, but it cannot be created or destroyed under ordinary conditions (i think you can’t destroyed an energy whatsoever)” Light bulb requires electricity to light, and what that means is electricity changed to light, for this case it also changed to heat,radiation, etc. After that, heat and light may change to another form or just simply displace, for example absorbed to our body, to things in our home. Therefore, energy cannot be destroyed neither created, it’s just simply changed from one form to another.
