How does an insulator prevent the flow of electricity?

Answer 1

It depends on what kind of insulators you are referring to. The ultimate purpose of an insulator, regardless of application, is to prevent or impair the conduction of energy.

Thermal insulation works primarily by trapping pockets of air in a cohesive layer of material (fiberglass or foam, usually) to prevent the movement and conduction of heat.

Sound/Vibration insulation can be similar to Thermal insulation, but can also make use of elastic or absorptive materials, like rubber or springs, that absorb sound and vibrations, again, to prevent the conduction of energy.

Electrical insulation is usually accomplished by using non-electrically conductive materials, like glass, some ceramics, some rubbers and plastics, to coat or isolate whichever electrical conductor is in question. This prevents the electrical energy from being conducted to undesirable locations.

Answer 2

The key factor that contributes to whether a material will conduct electricity or not is determined by structure of the valence and conduction band (i.e. bandgap) and resulting Fermi levels. In the case of conductors the valence band and conduction band overlap which is inherently why metals are good conductors. Generally electrons in the band fill to a certain level (Fermi Energy) and then bridge the bandgap (say in semiconductors) resulting in increased conductivity. The action of electrons moving from the valence band to the conduction band is what causes conductivity. Thus with overlapping bandgaps, metals are much more susceptable to this than say insulators with a very large bandgap. The more electrons that move to the conduction band, the better the electrical conductivity.

There is a lot of other theory surrounding electrical and thermal conductivity relating to phonon-phonon interaction and relaxation time given by the Drude model, but hoepfully this was a simple enough explanation.

Answer 3

Insulators are objects made from a certain material that don't conduct heat (heat can't run through it).

They are usually made of wood or plastic.

E.G. A wooden spoon is an insulator so that you don't burn yourself while cooking.

Answer 4

All atoms have electrons that orbit the nucleus, we are concerned with the outermost orbit. The outer orbit shell can have from 1 to 8 electrons. The fewer electrons an atom has in this orbit the better it is at conduction (one or two electrons, it is easy to knock one of the electrons out of orbit and pass to the next atom). The more electrons you have, the better it is at insulating. Nothing is a perfect insulator, if you apply enough voltage the electrons will move (current will flow). This is why the insulation on conductors have a voltage rating.

Answer 5

There are three types: conductors, semi conductors and insulators. For the conductors the valance band and conduction band are almost overlapping so a very less electrical energy is required to produce a current. But in insulators the forbidden gap is very high, so electrons can't jump from valance band to conduction band. It is very difficult to get a flow of current through an insulator, but if you apply very large voltage, which is greater than the breakdown strength of insulator, we will get a flow of current.

Answer 6

Electrons in the outer shells are not held tightly to single atomic nuclei and so are shared by neighbouring atoms this allows them to "wander" when an electric potential is put across the conductor. The electrons in the outter shell of atoms are known as valency electrons. They are the electrons that require the least energy in order to free them from the nucleus to which they are bound.

At the centre of a metal atom (and other atoms) is a positively charge nucleus, consisting of protons and neutrons (particles of positive and neutral charge respectfully). Around the atom, way out in the distance (in atom size terms) are electrons (as many as protons in a neutrally charged atom). The electrons in a metal are more weakly bound to the positive nucleus than in other atoms that don't conduct (remember positive and negative charges attract!). Electrons are a bit like gas molecules in the wire, in that they move randomly in all directions, and when a pd is applied they drift in the opposite direction of the pd, but continue their random motion as well. Why do they travel in the opposite direction as the potential difference? When people discovered electricity, they didn't know which way electrons flowed, or even that they were electrons! So we have conventional current, which flows from + to -, and we have the real current, which, because we know electrons are negative, and we know opposite charges attract, flows from the negative to the positive. The drift velocity can be very slow, but the electrons are moving in random directions very quickly. As a conductor heats up, its atoms begin to shake around, and this causes greater resistance, and greater lose of energy, hence superconductors are often kept at very low temperatures indeed!

Now, because there are electrons only weakly bound in metals, this means you don't need much energy to free them and make them go travelling down the wire. The energy to do this comes from a potential difference, for which the units are the volt (or joule per coulomb). This quantity is a measure of the amount of energy one coulomb of charge will get if it travels between two points down the wire or around an electrical circuit. The energy is supplied by a battery or a power generator, and we say it applies a potential difference across the wire, making the electrons move in the wire, and hence power is sent down the wire to another point. If you are at home waiting for energy to come down the wire, you don't have to wait for electrons to make it all the way from the power station, because they all push on each other, and in that way, the energy travels down the wire. (Alternating current is used in practice where the electrons move back and forth many times a second).

Current is a measure of the amount of charge that passes a point in 1 second, in coulombs per second, or amps. We know that the voltage is the amount of energy per charge, and we know that power is the amount of energy that passes per second, so we can say that voltage times current is the power that travels down the conductor: that's how much energy we are getting ever second!

On the subject of alternating current (AC): the electricity that comes out of the mains; and direct current (DC): the electricity that comes from a battery. Why would we chose AC over DC through a conductor that carries a high power over a long distance, such as the national power grid? well, AC operates on what is known as an alternating potential difference, where the force that is moving the electrons keeps changing in the opposite direction, as was stated above. We call this force the electro-motive force (EMF), and it is proportional to the potential difference. A DC current simply keep pushing the electrons in the same direction. Remember, it doesn't matter which direction the electrons are moving in (towards or away from you home), as you don't have to wait for electrons from the power station to arrive for you to get energy. But DC is necessary for many home applications, therefore this current is changed to DC later.

Going back to the fact that power=current times voltage, there is another way to express power value that is important, and that is the power dissipated in a conductor, and this takes the value current squared times the resistance in the wire, so you can see, that if we can increase the voltage and decrease the current, and still have the same power, so long as voltage times current is the same value, we get a massive bonus, because, whilst the resistance in the wire is related to how much energy will be lost to heat by being directly proportional to power dissipated, the power dissipated is actually proportional to the square of the current via p=I^2*R, were * simply means multiply, and this means that if we were to reduce the current down the wire, but increase the voltage (reduce the amount of charge being moved, but increase the energy per unit of charge), we could effectively send that same amount of power down the wire, but without sending as much charge. To do this a step-up transformer is used, which does the job of increasing the voltage without sending more power down the line.

Now, if you had a material that wasn't a conductor, as a copper wire, what would happen? it would take more energy to pull the electrons away from their atoms, and the result would be more waste, and more heat generated. That's why, if you put a large potential difference across a piece of plastic, eventually it would simply melt! That is also why people sometimes can get electrical burns.

You may have heard of a type of material called a semi-conductor? This is in-between a conductor and a resistor in terms of its willingness to allow charge to pass through it, and interestingly, unlike a conductor, the resistance, instead of being proportional to the temperature, is inversely proportional to the temperate, which means, the hotter it gets, the more easily current will flow. The exact reason a semi-conductor works, I believe, is beyond the scope of this question, however, in its useful form, it is a highly engineered material that workers by only allowing electrons of certain energies to flow. The semi-conductor materials are used in computers and LEDs.

Answer 7

Conduction:

Allows electricity to flow. Wires or copper tracks on a circuit board, allows electricity to flow from one component to another. The least resistance the better, although a compromise of cost comes into the factors determining the material used.

Insulation:

Does not conduct electricity. Insulators are used to cover wires to protect them from touching components or people, to prevent electric shock or short circuits. Insulators are also used to support components without interacting with the circuit supported or other parts.

Answer 8

The materials that do not conduct electricity are known as insulators. Insulators are used to cover the live wire, support the live wire etc.

Answer 9

Electrical insulators work by inhibiting the transmissions of electric current. Rubber is considered to be among the best electric insulators.

Answer 10

They are materials through which electric current does not pass easily.