0
\$\begingroup\$

All i know is electric current travels in a loop. So how / where in its way does electricity (electric energy) get wasted? And what do we do on switching electric appliances off? If it's not electric current that is wasted then what is it?

\$\endgroup\$
  • 2
    \$\begingroup\$ By "electricity" I presume you mean electrical energy. By "wasted" do you mean consumed? "Wasted" would generally mean energy that was lost in transmission or due to the efficiency losses in the end load. \$\endgroup\$ – Transistor Dec 24 '18 at 15:38
  • \$\begingroup\$ Unless you are using superconductors, the wiring has resistance and some energy is lost due to heat (from I^^2R losses) \$\endgroup\$ – Peter Smith Dec 24 '18 at 15:40
  • 2
    \$\begingroup\$ 'Wasting electricity' is generally used as a subjective term, not a scientific one. There, it means that the energy was consumed for no benefit e.g. leaving a light on in an unoccupied room, heating an empty house, dissipating heat unnecessarily in resistors. \$\endgroup\$ – TonyM Dec 24 '18 at 15:42
  • \$\begingroup\$ @TonyM I think it's pretty clear what he means. Unless he really does mean that the electrical energy is going off to parties and getting very, very drunk. Then I will grant you that I misunderstood. \$\endgroup\$ – TimWescott Dec 24 '18 at 16:42
  • 1
    \$\begingroup\$ The way my physics teacher put it is that we don't pay the electric company for electrons. We pay them for power. By pushing electrons back and forth in the electric wires, they heat our homes, run our motors, power our computers, etc. But no electrons are gained or lost in the process. \$\endgroup\$ – mkeith Dec 24 '18 at 21:22
3
\$\begingroup\$

You are confusing electrical current with electrical energy. Given how you express confusion over the fact that current can go in a loop yet energy is wasted, I think that you are also tied to the notion that energy must be tied to the matter that happens to be carrying it.

Yes, current goes in a loop. We do not, on an everyday basis, create or destroy electrons*, and electrons strongly repel each other and are strongly attracted to atomic nuclei, so any current that flows is forced to loop around and come back to the source. This does not mean that energy does not flow, however. If I connect a battery to a pair of wires here, then the battery adds energy to any electrons flowing through it from its positive electrode to its negative electrode. This potential energy per electron is seen as the voltage of the battery. If those wires are connected to a light there, then current will flow through the light. The energy imparted in those electrons in the battery will be converted to light and heat in the light. If you ignore any losses in the wires, then the energy has flowed from the battery to the light, but the net number of electrons has stayed pretty much the same everywhere.

If you're still caught up in the "how can electrons go in a loop but the energy goes from point A to point B" problem, then consider hydropower. The sun shines on the sea. It imparts energy to the seawater, some of which evaporates. Some of that blows over mountains, and some of that rains down. Some of that forms into a river, which someone has dammed. The water impounded behind the dam is run through turbines generating mechanical energy. Then the water runs back into the sea. The water has gone in a loop. The energy has been transported (with great inefficiency) from the surface of the ocean to the turbines in the dam.

Dunno if this helps -- it's always hard to know what will clear up a confusion.

* Please, please do not bring beta decay into this discussion. Yes, electrons are created. No, it is not on topic.

\$\endgroup\$
1
\$\begingroup\$

Electrical energy is usually generated by conversion of some other form of energy. This could be mechanical (a generator), chemical (a battery), light (solar panel), etc.

When we use electrical energy the energy is drawn from the source. If you pedal your bike (maybe 150 watts) and turn on the 3 W dynamo lights then that extra 3 W load will cause the speed of the bike to drop a little unless you input some extra energy. When the lights are switched off you can relax a little.

In the case of the bicycle dynamo some energy will be lost (probably what you mean by "wasted") in the dynamo (it's actually an alternator) some in the resistance of the wiring and some in the conversion of electrical energy to light. The most efficient LED lights, for example, are about 40 to 50% efficient so half of the energy is converted to useful light and the other half given off as heat which is generally "wasted" although if it contributes to keeping your igloo warm it might be considered useful energy consumption. When you switch on a load in your house the power station is loaded that little bit more but the automatic governor will increase the fuel into the engine (or whatever) to increase the power input to match the load.

And what do we do on switching electric appliances off?

When a device is switched off no current will flow and no energy will be consumed. The generator or battery will experience a reduced load.

\$\endgroup\$
1
\$\begingroup\$

Some energy loss is unavoidable. That energy loss is really not waste, it is part of the cost of providing some benefit in a convenient way when and where we want it. On average, something like seven percent of the electrical energy transmitted to consumers by power stations is dissipated as heat in transmission. That could be reduced by building power stations closer to the consumers and by building more expensive transmission and distribution systems. However people don't like to live near power stations and expensive transmission systems add to the cost of power. Therefore we consider whatever energy loss is required to deliver the energy as a necessary loss or cost and not a waste.

In general, we consider that every energy loss is a necessary cost and not a waste if the energy is gives us something useful or necessary and the loss can not easily and inexpensively be reduced. Whenever technology provides means of reducing energy loss, we consider it to be wasteful not to adapt it once it has been shown to pay for itself in energy savings within a reasonable period of time.

However, each person uses their own judgement as to what is a necessary use of energy and what is a waste. We may or may not consider the advice of others.

\$\endgroup\$
0
\$\begingroup\$

This is a bit of a simplistic answer.

Imagine rolling a ball down a hill into a wall. When it hits the wall its energy is lost as heat/sound. Push the ball back up the hill and let it go again. Pushing it up the hill has instilled it with energy and that energy, once again is lost when you push it down the hill and it hits the wall.

You could do this over and over again and this could be seen as electrons circulating but, to return an electron from 0 volts to a higher voltage (the top of the hill) requires energy to be imparted to that electron. The same with the ball - pushing it to the top of the hill requires energy.

That imparted energy (to raise it) is lost once the electron travels through a resistive load and back to 0 volts (fallen). Energy is wasted.

\$\endgroup\$
-1
\$\begingroup\$

One of my neighbours had the heating and the air conditioner on at the same time. Another neighbour had a very bright outside light on day and night for as couple of weeks. They wasted electricity.

To reduce wasted electricity my city gave me LED light bulbs for free to replace incandescent and compact-fluorescent light bulbs. My city also gave me a high efficiency refrigerator for free to replace my old power hungry refrigerator.

\$\endgroup\$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.