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HOW MUCH ELECTRICITY DOES A LAMP USE?

When electricity flows through a lamp filament, it gets changed entirely into light. Yet not one bit of electricity is ever used up by the light bulb, and all the electricity flows out of the filament and back down the other wire

Light bulbs don't consume 'electricity'. Instead, the charges of the thin lamp filament are forced to flow along much faster than they would in thicker wires, and this heats the filament because of a sort of 'electrical friction'. Charges are flowing into the bulb through one terminal, but then they flow back out again through the other terminal.

The quantity of charges inside the filament doesn't change, and none are used up.

This does not mean the electricity is free - See next question:

When you see an advertisement where the electric company says that they're making or selling electricity, what's going on?

Simple: they're using an UNSCIENTIFIC definition of the word 'electricity'.

Power companies really don't sell any electricity. Instead they sell a pumping service; they're just pumping electricity back and forth inside the wires. That's what Alternating Current (AC) means. The electricity just sits in the wires and wiggles 50 times (in Australia), per second.

Since power lines use Alternating Current (AC), the electrons really don't leave the wire, or even move much at all while they are in it.

Instead they sit in one place inside the wires and vibrate back and forth. (It's somewhat like sound: the sound waves move fast, but the air molecules just vibrate back and forth without flowing forwards from the source of the sound out into the distance.)

The electric company sells a pumping service, and you can use their service to run motors and heaters and light bulbs.

Then what does the electric company bill us for - especially since it takes back all of the electrons it gives us?

Imagine this: if electric motors and generators had never been invented, then the “Power Company” could use water instead. The water would be inside a long, long loop of hose, and when the 'Water Power Company' pumped the water, you could attach their hose to a water motor, and the motor would turn. The water inside the hose would serve as a long drive belt. The water would stay inside the circle of hose, and it would be pumped around the loop over and over again. And when you opened the valve, your motor would turn on instantly, even though the water might be flowing quite slowly. (When you remove the blockage, the whole loop of water starts flowing at once.)

Many years ago, before motors and generators were invented, 'power companies' used leather drive belts and rotating drive shafts to send energy to their customers. This really happened, although their customers at that time were not spread out in the suburbs like they are now.

Back then, the power company customers were all in the same area, and the “power company” was just a huge steam engine located in the middle of each factory. Energy was sent to all of the factory machines using long leather belts and metal drive shafts. I guess you could say that these old factories ran on 'Mechanicity' instead of 'Electricity'.

It may surprise you to know that even today, we still use steam engines to pump electricity; although today, many are powered by nuclear reactors as well as coal, oil or hydro (water wheels).

Electric wires and electric motors aren't so incredibly 'modern' as the power companies might want you to think: They are really just one way of hiding all the leather belts that connect all the factory machines to a big steam engine located somewhere in the distance!

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• Generators don't produce 'electricity', they produce 'electrical energy'.
• Electrical energy consists of invisible fields resembling radio waves that whiz along OUTSIDE the wires.

Generators are 'charge pumps'. They force the 'charges' found INSIDE the wires to flow along.

In case you find this all very confusing and/or challenging, then more detailed explanation is included in the answers and references found in the next sections (SCIENTIFIC EXPLANATION and MISCONCEPTION) and in the SCIENTIFIC EXPLANATION sections for this and the next four questions in this QUIZ.

MISCONCEPTION: Electricity that is generated at the power station flows inside metal wires to power outlets in homes and businesses, where it is used up by lamps and other electrical appliances.

CORRECT UNDERSTANDING: In DC circuits and in 50Hz AC circuits (including 240V and higher domestic & commercial power in Australia), the 'current' exists all through the entire wire.

Electronics students commonly assume that this means electrical energy flows INSIDE the metal wires, but this is not right.

Physics students have a different understanding.

The scientific explanation is that electrical energy normally doesn't flow inside of metals. In fact, the 'joules' being sent out by batteries and generators are located in empty space: they take the form of electromagnetic fields surrounding the wires.

Similarly, batteries don't supply 'electricity' - the wires themselves supply that from their own substance.

A battery is a chemically-fuelled 'charge pump'. Like any other kind of pump, a battery takes charges in through one connection and spits them out through the other.

A battery or a generator is NOT the source of the substance or 'stuff' being pumped.

As per this reference: A. Sommerfeld (1952) has pointed out, metals are good conductors of CURRENT but non-conductors of ENERGY.

Metals conduct CURRENT but space conducts ENERGY and the best conductor of electromagnetic (EM) ENERGY is the vacuum!

When we turn on a lamp or other electrical device from a remote switch, we don't have to wait for electrons to complete a journey because the electrons are not given the ENERGY in the first place.

There are two valid schools of thought about how one should conceptualise energy and energy transfer, that I will call:

• the 'accountant’s model'
• and the 'field model'.

The accountants view energy solely as a mathematical attribute of physical systems, and it does not need any kind of conceptual model beyond that.

The story of energy transfer from the battery to the globe goes like this. When the battery is first connected to complete the circuit it pushes electrons (charge) around so that they pile up on the surfaces of some parts of the circuit, leaving a deficit of electrons, and hence a positive charge on other parts of the conductors’ surfaces. This pushing around of electrons is mediated by the electric field. The charge separation in turn produces electric field inside the connecting wires as well as in the wire filament of the light globe.

The internal electric field is directed along the axis of the wires and is responsible for producing a drift of mobile charge carriers, current, in the wires.

To explain energy transfer we need to look at what is happening outside the wires.

As a consequence of the surface charges on the wires, there is an electric field in the space outside the wires (as well as inside).

Also, as a consequence of having a current in the wires, there is a magnetic field in the space around the wires. It is this combination of electric field and magnetic field in the space outside the wires that carries the energy from battery to globe.

Once the fields are set up, the energy travels through space, perpendicular to both the electric field and the magnetic field, at the speed of light.

Energy leaves through the sides of the battery and enters the wire of the globe through the sides of the wire. As Arnold Sommerfeld (1952) has pointed out, metals are good conductors of current but non-conductors of energy. Metals conduct current but space conducts energy and the best conductor of electromagnetic energy is the vacuum!

Reference: Science Teachers’ Workshop 2002 Understanding Circuits What the Text Books Don’t Tell You - Ian M. Sefton School of Physics, The University of Sydney

Reference: Energy transfer in electrical circuits: A qualitative account - 2005 The application of the surface charge model to a simple circuit shows that electromagnetic energy flows from both terminals of the battery, mainly in the vicinity of the wires ~and not inside them! to the load where it enters and is converted into heat at a rate obtained from Ohm’s law. © 2005 American Association of Physics Teachers.

http://sites.huji.ac.il/science/stc/staff_h/Igal/Research%20Articles/Pointing-AJP.pdf Also see: IN A SIMPLE CIRCUIT, WHERE DOES THE ENERGY FLOW?