does the light bulb violate the conservation of energy law?

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.

(if you want to take this to the next level, think about atomic bomb, or assume that in our earth there's fixed amount of energy that constant)

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 "lost" energy. We can rate our light bulb by measuring its efficiency, or percentage of energy that goes where we want it to go.

Even though we may "lose" energy in the form of heat, the total energy is still the same. Energy is conserved. So, if all energy is conserved, we can never run out of energy! Right? As we will see, our lives and the lives of energy are not that simple.

Nope... nothing violates that law. Otherwise, we'd have to arrest it. ;-}

Seriously... the total energy of the bulb TE = LE + QE = I*V dt; where LE is the energy converted to light, QE is the energy converted to heat, and I is the direct current and V is the voltage. IV dt is the input total energy to the bulb. dt is the time the bulb is burning (on).

As you can plainly see, all the energy put into the bulb is accounted for. None has been destroyed. What has happened, though, is that some of the TE was converted into useful energy, LE, while the rest was converted into useless energy, QE. We assume light not heat is the purpose of the bulb in this case. There are, of course, infra red lamps to keep food warm, for example, where QE would be the useful energy and LE the useless. Depends.

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.

What makes you think it does?

Electrical energy is changed to heat and light in the bulb.

nope , of course not

NO