String Trimmer Batteries - same weight charged and empty

[T.G.G. Moogly]

I weighed these guys empty and fully charged. There are two different batteries, one is stronger and heavier so it lasts longer. But when I weigh each battery fully charged and empty it's weight doesn't change, at least to the nearest gram. Do I need a more precise scale?

I know electrons have no mass so is that the answer?

Okay, so I googled and found that the electrons just move, they don't leave the battery as electricity. Cool.

 

[skepticalbip]

nm

 

[bilby]

Electrons do have mass (I didn't even know that they were catholics); But electricity isn't electrons - it's the movement of electrons. And they move quite slowly - the drift velocity of electrons in a standard domestic copper wire at 15 Amps is only about walking pace - and it's alternating current, so they don't flow into or out of your home - you pay the electric company to jiggle the electrons that you already own, they don't give you any new ones.

In a battery, electrons flow from one side to the other as the battery discharges; Then when you recharge it, you push them back to where they started. The total number of electrons doesn't change, so their mass isn't relevant. The energy of a charged battery does appear as mass, in accordance with Einstein; But as c is a huge number, and c² is the square of a huge number, and E=mc², you need a metric fuckton of E before you get a measurable amount of m.

A 12V, 15Ah battery stores 648kJ of energy. 648kJ masses about 350 nanograms, or 0.35 micrograms (a hundred millionth of an ounce, for those watching in black and white) - You will need some VERY sensitive scales to detect that. If you leave a fingerprint on the battery, it's going to outweigh the mass gain from recharging it.

 

[barbos]

A 12V, 15Ah battery stores 648kJ of energy. 648kJ masses about 350 nanograms, or 0.35 micrograms (a hundred millionth of an ounce, for those watching in black and white) .

Check your math, cause it's less than what you got.

 

[bilby]

A 12V, 15Ah battery stores 648kJ of energy. 648kJ masses about 350 nanograms, or 0.35 micrograms (a hundred millionth of an ounce, for those watching in black and white) .

Check your math, cause it's less than what you got.

I have just finished a(nother) twelve hour day and a(nother) six day week. Given how tired I am, I wouldn't be at all surprised if I have dropped several orders of magnitude. I have a tendency to do that even when I am fully compost-mentis.

Suffice to say, the mass involved is far too small to measure with a domestic balance that has divisions of plus or minus 1g

 

[barbos]

A 12V, 15Ah battery stores 648kJ of energy. 648kJ masses about 350 nanograms, or 0.35 micrograms (a hundred millionth of an ounce, for those watching in black and white) .

Check your math, cause it's less than what you got.

I have just finished a(nother) twelve hour day and a(nother) six day week. Given how tired I am, I wouldn't be at all surprised if I have dropped several orders of magnitude. I have a tendency to do that even when I am fully compost-mentis.

Not several, merely 1.68613444433554 orders of magnitude

I did not know slavery was still legal in Australia.

 

[steve_bank]

That is actually not a bad question. The Laws Of Thermodynamics have to apply.

Consider recharging a plain old lead acid battery. Plates immersed in an electrolyte. What happens is the reversal of a chemical process. Heat is generated because the reversal process is not 100% efficient.

You should be able to look up lead acid battery.

 

[Bronzeage]

Okay,

Two similar flashlights are on opposite pans of a balance beam scale. Weight is added to bring the flashlights to exact balance. One flashlight is turned on and left to shine until the battery is disharged.

Are the two flashlights still in balance?

 

[steve_bank]

Laws of thermodynamics must apply, the starting point on any energy-mass problem.

Consider a charged battery. Put a bulb across it and energy is consumed X watts are used.

To restore the battery to the same state x + %efficiency must be added via current through the battery.

The short answer is I do not know off the top of my head, like I said it is a good question. I am weak in chemistry. You can look up the equations on the net for a simple common battery. The chemical charge and discharge equations will show energy and mass balances.
\
Offhand I'd say the weight remains the same. because of conservation. Put a bulb across a battery and the electrons leaving one terminal must equal the number of electors returning through the other terminal. If not you would be creating or destroying energy in the bulb.

 

[barbos]

Offhand I'd say the weight remains the same. because of conservation. Put a bulb across a battery and the electrons leaving one terminal must equal the number of electors returning through the other terminal. If not you would be creating or destroying energy in the bulb.

There is no law of conservation of mass, there is a law of conservation of energy.
So correct answer is "Yes, charged battery is a tiny bit heavier".
Charged capacitor is heavier because electric field in charged capacitor has energy, hence mass.
With batteries, they they change their chemical composition when charged/discharged, which again corresponds to change in total energy.

 

[bilby]

Laws of thermodynamics must apply, the starting point on any energy-mass problem.

Consider a charged battery. Put a bulb across it and energy is consumed X watts are used.

To restore the battery to the same state x + %efficiency must be added via current through the battery.

The short answer is I do not know off the top of my head, like I said it is a good question. I am weak in chemistry. You can look up the equations on the net for a simple common battery. The chemical charge and discharge equations will show energy and mass balances.
\
Offhand I'd say the weight remains the same. because of conservation. Put a bulb across a battery and the electrons leaving one terminal must equal the number of electors returning through the other terminal. If not you would be creating or destroying energy in the bulb.

It's not a closed system. Energy leaves the bulb to the environment in the form of light and heat (heat being dominant in the case of an old-school incandescent bulb).

A sufficiently sensitive balance could measure the change in mass, but as discussed above, the change is minuscule. An ordinary pan balance would likely not respond to the change as it would be far too small to overcome the friction in the components of the balance. We are talking nanograms here. One joule masses 1/c²kg - and c² is in the order 10¹⁷m²s^-2, so even hundreds of kJ won't contribute much to the mass of the battery. It's not zero, but it's not enough to measure with household equipment.

 

[Loren Pechtel]

Okay,

Two similar flashlights are on opposite pans of a balance beam scale. Weight is added to bring the flashlights to exact balance. One flashlight is turned on and left to shine until the battery is disharged.

Are the two flashlights still in balance?

No, but I don't believe there is a scale sensitive enough to detect this. E = mc^² applies no matter how the energy is stored. Your watch gets heavier when you wind it and lighter as it runs. (I strongly suspect wear on the metal exceeds this, though.)

 

[steve_bank]

Offhand I'd say the weight remains the same. because of conservation. Put a bulb across a battery and the electrons leaving one terminal must equal the number of electors returning through the other terminal. If not you would be creating or destroying energy in the bulb.

There is no law of conservation of mass, there is a law of conservation of energy.
So correct answer is "Yes, charged battery is a tiny bit heavier".
Charged capacitor is heavier because electric field in charged capacitor has energy, hence mass.
With batteries, they they change their chemical composition when charged/discharged, which again corresponds to change in total energy.

LOT is unconditional in electricity and electronics. Current in one terminal must equal current out the other for any form of sources. Any exception would be Nobel material.

Again to absolutely prove it one way or another you have to go through the chemical equations that show energy and mass. Jn thermodynamics it is called a continuity equation, where mass and energy comes from and goes to in any process.

If you want to seriously debate whether LOT applies in the case of a battery then you are into the realm of pseudoscience..

Energy in the bulb shows up as an energy debit in the battery. It would be the same for a simple resistor. The resistor heats up and increases thermal radiation. An incandescent bulbis thermal black body radiation. Electrons are not consumed.

If you measure current on one side of the bulb or a resistor and it is different than the other side that would be worth a paper. The bulb is an ohmic resistor. A piece of wire.

 

[barbos]

Offhand I'd say the weight remains the same. because of conservation. Put a bulb across a battery and the electrons leaving one terminal must equal the number of electors returning through the other terminal. If not you would be creating or destroying energy in the bulb.

There is no law of conservation of mass, there is a law of conservation of energy.
So correct answer is "Yes, charged battery is a tiny bit heavier".
Charged capacitor is heavier because electric field in charged capacitor has energy, hence mass.
With batteries, they they change their chemical composition when charged/discharged, which again corresponds to change in total energy.

LOT is unconditional in electricity and electronics. Current in one terminal must equal current out the other for any form of sources. Any exception would be Nobel material.

Well, LOT does not have law of conservation of mass, it has law of conservation of energy.

Again to absolutely prove it one way or another you have to go through the chemical equations that show energy and mass.

To prove? what is there to prove? mass is not really that useful concept in physics anymore. Mass is a CM (Center of Mass) energy of a system, nothing more, it obviously does not conserve if system is not closed.

Jn thermodynamics it is called a continuity equation, where mass and energy comes from and goes to in any process.

If you want to seriously debate whether LOT applies in the case of a battery then you are into the realm of pseudoscience..

What the fuck are you trying to convey here? I told you the correct answer - charged battery weighs more than before charging.
And if you can prove otherwise then it's you who should be getting Nobel Prize, not me.

 

[steve_bank]

LOT is unconditional in electricity and electronics. Current in one terminal must equal current out the other for any form of sources. Any exception would be Nobel material.

Well, LOT does not have law of conservation of mass, it has law of conservation of energy.

Again to absolutely prove it one way or another you have to go through the chemical equations that show energy and mass.

To prove? what is there to prove? mass is not really that useful concept in physics anymore. Mass is a CM (Center of Mass) energy of a system, nothing more, it obviously does not conserve if system is not closed.

Jn thermodynamics it is called a continuity equation, where mass and energy comes from and goes to in any process.

If you want to seriously debate whether LOT applies in the case of a battery then you are into the realm of pseudoscience..

What the fuck are you trying to convey here? I told you the correct answer - charged battery weighs more than before charging.
And if you can prove otherwise then it's you who should be getting Nobel Prize, not me.

Adios chico. mass and energy are fundamental units That underlay all sconce.

 

[steve_bank]

Consider a water task filled with water. A pipe connects it to a turbine and then to another tank. A valve is opened, the turbine turns a generator that does work. Work is done. The total mass of the water in the system does not change.

A battery creates a potential difference in volts across the terminals. Put a wire across it and there is a pressure or force across the wire in Newtons/meter. An electric field that pressurizes the wire. No different than pressurizing a water pipe.

The electrons do work, force times distance. The thermal photons come from the atoms not create the electrons. The electrons do work on the atones. It is called resistance for short. The work done by the electrons shows up as an energy deficit in the battery.

 

[barbos]

Adios chico. mass and energy are fundamental units That underlay all sconce.

Maybe all sconce, but not science. And energy and mass are not units,

 

[barbos]

Consider a water tahk filled.....

Dude, give yes/no answer to OP question.

 

[bilby]

Offhand I'd say the weight remains the same. because of conservation. Put a bulb across a battery and the electrons leaving one terminal must equal the number of electors returning through the other terminal. If not you would be creating or destroying energy in the bulb.

There is no law of conservation of mass, there is a law of conservation of energy.
So correct answer is "Yes, charged battery is a tiny bit heavier".
Charged capacitor is heavier because electric field in charged capacitor has energy, hence mass.
With batteries, they they change their chemical composition when charged/discharged, which again corresponds to change in total energy.

LOT is unconditional in electricity and electronics. Current in one terminal must equal current out the other for any form of sources. Any exception would be Nobel material.

Again to absolutely prove it one way or another you have to go through the chemical equations that show energy and mass. Jn thermodynamics it is called a continuity equation, where mass and energy comes from and goes to in any process.

If you want to seriously debate whether LOT applies in the case of a battery then you are into the realm of pseudoscience..

Energy in the bulb shows up as an energy debit in the battery. It would be the same for a simple resistor. The resistor heats up and increases thermal radiation. An incandescent bulbis thermal black body radiation. Electrons are not consumed.

If you measure current on one side of the bulb or a resistor and it is different than the other side that would be worth a paper. The bulb is an ohmic resistor. A piece of wire.

The laws of thermodynamics apply to closed systems. A flashlight is not a closed system - energy departs from the system both as heat and as light when the flashlight is switched on; And it enters the system from an external power source when the batteries are charged or replaced.

 

[fromderinside]

The laws of thermodynamics apply to closed systems. A flashlight is not a closed system - energy departs from the system both as heat and as light when the flashlight is switched on; And it enters the system from an external power source when the batteries are charged or replaced.

https://www.britannica.com/science/thermodynamics/Open-systems

Open Systems


Thermodynamic potentials

Most real thermodynamic systems are open systems that exchange heat and work with their environment, rather than the closed systems described thus far. For example, living systems are clearly able to achieve a local reduction in their entropy as they grow and develop; they create structures of greater internal energy (i.e., they lower entropy) out of the nutrients they absorb. This does not represent a violation of the second law of thermodynamics, because a living organism does not constitute a closed system.

In order to simplify the application of the laws of thermodynamics to open systems, parameters with the dimensions of energy, known as thermodynamic potentials, are introduced to describe the system. The resulting formulas are expressed in terms of the Helmholtz free energyF and the Gibbs free energy G, named after the 19th-century German physiologist and physicist Hermann von Helmholtz and the contemporaneous American physicist Josiah Willard Gibbs. The key conceptual step is to separate a system from its heat reservoir. A system is thought of as being held at a constant temperatureT by a heat reservoir (i.e., the environment), but the heat reservoir is no longer considered to be part of the system.

Not disagreeing just 'splaining