What are Solids?
One of the four essential states of matter is solid (the others being liquid, gas and plasma). In a solid, the molecules are packed tightly together and have the least amount of kinetic energy. Structural stability and resistance to a force applied to the surface characterise a solid. A solid material, unlike a liquid, does not flow to take on the form of its container, nor does it expand like a gas to fill the entire volume available.
There are physical as well as electrical properties of matter. Likewise, solids have definite shape and volume. However, depending on their composition and chemical structure, the electrical properties of solids differ to a large degree. Conductors, semiconductors and insulators are classified into three categories.
Electrical Properties of Solids
Conductivity is referred to as the electrical property of a material. A substance's electrical conductivity is characterised as its capacity to transmit heat energy or electrical energy (and in some cases also sound energy). Thus a good electricity conductor can easily transmit energy without boiling, melting or altering its composition in some way.
Solids have different degrees of conductivity, which means that all solids do not have uniform electrical properties. Currently, based on their electrical conductivity, solids can be classified into three different categories. The following are these three categories:
Conductors
Conductors are solids that have strong electrical conductivity. They allow heat energy and electric currents to transmit with ease and speed through them. Conductors allow this energy transfer to take place through free electron flow from atom to atom. When the current is just applied to one part of their body, they have the power to bring this energy all over themselves.
The strongest conductors are understood to be all metals. Their conductivity is dependent on their atoms' number of valence electrons. Such electrons are not tightly bound together and are free to pass. Metals have electrons like this in their atoms, which is why they conduct heat and electricity so well. Metals allow the electric field to transmit in conductivity ranges from 106-108 ohm-1 through them.
Insulators
Unlike conductors, insulators are materials that do not conduct any electrical energy or currents at all. They do not allow any electric charge (or very little) to pass through them. They have a considerable bandgap that prevents electricity from flowing. Glass, wood, plastic, rubber, etc. are some examples.
Since insulators are very weak conductors, there is another use for them. In order to insulate conductors and semiconductors, we use them. You would have seen copper wires, for instance, covered with plastic or some sort of polymer. Without allowing the electric current to go through them, they secure the wires and cables. This is wire insulation.
Semiconductor
The one between conductors and insulators are semiconductors. These are solids that have the ability, but only under certain conditions, to conduct electricity through them. The ability of semiconductors to conduct energy, heat and impurities is impaired by two such conditions.
Intrinsic Semiconductor: These are pure materials, so they are classified as undoped semiconductors with no impurities added. We add thermal energy to the material here and create vacancies in the bands of valence. This makes it possible for the energy to move through. Yet, these conductors are not very strong and have very few applications Extrinsic Semiconductors: These are semiconductors with doping. To boost the conductivity of the products, we add some impurities. There are two kinds of extrinsic semiconductors: n-type and p-type, respectively. Examples are that through this technique, we increase the conductivity of silicon and germanium.
Semiconductors are the most important material due to its property that one can control the conductivity of semiconductors. Due to this reason, semiconductors are mostly found in electronics applications.
Thermal conductivity is nearly related to the electrical conductivity of a substance. We know that metals are good electrical conductors. For a solid to conduct heat, one molecule or atom movement needs to be easily transferred to its neighbour. This type of transfer is relatively easy because of the non-directional nature of the metallic bond, so metals conduct heat well. In a solid network, on the other hand, where the bonds are stiffer and the angles between the atoms are strictly defined, it is more difficult to transfer them. These solids are expected to have low heat conductivity and are known as heat insulators.
FAQs on Electrical Properties of Solids
1. What are the physical and chemical properties of solids? State the types of solids.
The physical and chemical properties of solids are as follows:
A solid has a fixed structure, shape, and volume. This means that neither of these aspects change as all the atoms in a solids are packed tightly together in a set arrangement.
A solid has a relatively high density.
Its intermolecular forces are quite strong.
Its particles are incompressible.
A solid tends to have a high melting point.
It has the ability to resist a force which is applied either parallel or perpendicular to a given surface.
There are three main types of solids. They are as follows:
Crystalline Solids: Their degree of order in a periodic atomic arrangement tends to be very high. Examples include diamonds, quartz, mica, and even snowflakes.
Noncrystalline Solids: unlike crystalline solids, these don’t have atoms and molecules organised or put together in a definite lattice-like structure. They are also known as amorphous solids. Examples include plastic, glass, fused silica, metallic glass, etc.
Quasicrystalline Solids: these have a quasiperiodic arrangement of atoms in them, which refers to patterns that don’t repeat at regular intervals. These tend to represent a fivefold symmetry which is normally forbidden in crystals. Alloys are very common examples of such solids.
2. Explain how solids are good conductors of electricity.
The particles present in a solid are closely packed together in a set arrangement which means that their location is fixed. The force between the adjacent particles is also high which makes it all the more effective for the heat to transfer and pass by during collision.
Solids tend to have a great electrical conductivity, which is why they’re also known as conductors. They allow both heat as well as electricity to pass through them with utter ease. This is mainly due to the fact that their conductivity is broadly dependent on their atoms’ number of valence electrons.
3. Differentiate between conductors and insulators.
The difference between conductors and insulators is as follows:
Conductors | Insulators |
These allow the flow of current through them. | These don’t let the flow of current pass through them. |
They have a very low resistance power. | They have a very high resistance. |
They have a high heat and electricity allowance. | They have almost no heat and electricity allowance. |
These aren’t known to store any energy when kept in a magnetic field. | When kept in a magnetic field, these tend to store energy. |
These are utilised in the production, application, and mechanism of various electrical equipment. | These are used for insulating various types of electrical devices for security and safety purposes. |
For example: copper, aluminium, etc. | For example: wood, paper, etc. |
4. What does the electrical conductivity of an object depend on and how does an increase in temperature affect it?
The electrical conductivity of an object depends on the ability of its electrons to move within the lattice-like structure of the material. If the electrons or other charge carriers of the said object are able to move freely within the lattice, then it is considered to be a good conductor of electricity.
The conductivity of an object is directly proportional to temperature, which means that the former tends to increase with an increase in the temperature as it is often affected by the nature of the ions. As the temperature increases, the ions start to move about faster as their kinetic energy increases.
However, the electrical resistivity tends to decrease with a decrease in the temperature.
5. Discuss about the conductivity of semiconductors.
At low temperatures, semiconductors tend to act like insulators and at higher temperatures, they act like conductors. This is because the electrons that gather around the atoms of the particular semiconductor are able to break away from their covalent bonds with a rise in temperature. That in turn lets the electrons move about freely in the lattice. And at room temperature, there are enough free electrons in a semiconductor to let it conduct some kind of current. So, it is safe to say that although the electrical conductivity of a semiconductor isn’t nearly as high as that of metals, but it isn’t as low as that of insulators either.
6. The Conductivity of Semiconductors Increases with an Increase in the Temperature? Is this Statement True or False? Give a Reason for the Same.
The given statement is true and explained below:
The motion of electrons is the explanation for the electrical conductivity of solids.
The lack of vacancies and other flaws is due to the conduction of ionic solids. Thus the conductivity of semiconductors is mostly due to impurities and defects found in them. In these solids, electrons and holes formed by the ionisation of defects lead to conduction. With the temperature, the electrical conductivity of semiconductors increases because the number of electrons from the valence bond will leap to the conduction band in semiconductors with an increase in temperature. Intrinsic semiconductor; with temperatures going up, conductivity goes up or resistivity goes down. Heavily doped conductivity turns up again or with temperature increase, resistivity goes down.
