Art of Making Electrons Work

The Atom

All matter in the universe is made up of tiny particles. Some particles are positive and some are negative. These particles are constantly jiggling around. When like particles come closer they repel each other with a great force, called the electric force. But the opposite particles attract each other. However an evenly mixed bunch of these particles will pull each other with great attraction and balance each other out.

This bunch of particles held together with the electric force is called the Atom. The positive particles are the protons and the negative electrons. Atoms also consist of other particles called the neutrons. But they have no charge.

Protons are heavier than electrons but they both have opposite charges of the same magnitude. In an atom the number of protons are usually the same and hence the atom has a net negative charge. However, when an atom loses electrons it becomes positively charged due to more protons than electrons. Similarly, when it gains more electrons it becomes negatively charged. Charged atoms are called ions.

The number of protons in an atom determines which element it is. It is called the atomic number (Z). It never changes for the same element. If the number is different it is a different element.

When atoms with opposite charges come closer they also get attracted by the electric force. They bond to become stable. They are called molecules. Charged atoms can bond with the atoms of the same element or with different elements. For instance, oxygen atoms bond with hydrogen atoms to form water molecules and with carbon to form carbon monoxide or carbon dioxide molecules and so on.

A number of atoms of various elements can bond together in complex combinations to gain stability. However not all elements bond with all other elements. It would be fair to say that some elements are particular with whom they want to bond.

Static electricity

When an atom gains electrons, it gets negatively charged. What happens when a lot of negatively charged atoms gather. They will constantly get repelled by like charged atoms. When they come in contact with another surface they will attract the positive charges on that surface. This attraction and repulsion will go on until all charged particles bind with other charged particles and there is a net neutral charge. We say that the system has found a balance.

This phenomenon is what causes lightning. When negatively charged clouds come close to the ground the positive charges in the ground get attracted and rise up. The attraction is so intense that there is a rapid movement of electrons through the air towards the ground. This sudden movement of electrons is called a static discharge.

Static discharge in a lightning heats up the air rapidly releasing energy as light. The rapid expansion of air causes the thunderous sound.

This is called static electricity, “static” (at rest) because it is not continuously moving. It will wait until it comes close to an oppositely charged surface and exchange electrons to stabilize.

Conductivity

Atoms of elements like copper can easily part away with electrons from its surface. We can free up as many electrons as there are atoms in a copper wire. We can use the electrical force to pull or push the electrons from the atom. We can attract it with a positive charge or repel it with a negative charge.

However, the electrons closer to the protons in the core are difficult to remove. The electric force behaves like the force of gravitation. It gets stronger the closer we get and weaker as we move away. The only difference is that gravity is only an attractive force whereas electric force is both attractive and repulsive.

Atoms are arranged in different ways in different elements and also vary depending on the state of the elements. Elements whose atoms can easily part with their electrons are called conductors. As we will see further we can make electrons move inside these conductors by attracting and repelling them between oppositely charged surfaces.

Similarly, electrons in atoms of some other elements are very difficult to remove. The electrons and protons are held together with very strong electric force in perfect harmony. These types of elements do not allow electrons to flow and can be used to restrict the flow of electrons. Hence they are called insulators.

Flowing electrons

Imagine two surfaces, one is positively charged and the other is negatively charged. When we connect these surfaces with a good conductor like the copper wire, the electrons from the positively charged surface will attract electrons from the copper. The end of the copper wire close to this surface will start losing electrons and become positively charged and in turn try to get an electron from the neighbouring atoms to find balance. It will look like the positively charged surface is trying to suck electrons from the wire.

Similarly the negatively charged surface will try to repel electrons. The end of the copper wire closer to this surface may lose its electron and gain some from this surface or its neighbouring atoms. It will look like the negatively charged surface is pushing electrons.

This pulling from one end and pushing from the other will go on until the entire system finds a balance. If the charge on both the surfaces are strong enough and the length of the copper wire is just right, the electrons from one end may travel all the way to the other causing a current of electrons.

Making electrons work

If we can keep the above two oppositely charged surfaces from finding balance by continuously taking away electrons from the positively charged surface and continuously replenishing electrons at the negatively charged surface, we can have a continuous flow of electrons through the wire.

When we move an object from one place to the other we say that “work” is done. In order to move that object we need to apply some force. Depending upon the size, weight, etc. of the object the force required will be more or less.

Similarly, in the case of electrons work is done by applying electric force to move them from negatively charged surface to the positively charged surface. In doing this work energy is released in the form of heat. Speed of electrons We now know how to move electrons through a conductor. But at what speed do they move? The short answer is that they move very slow.

Free electrons in conductors are constantly moving or jiggling if you may. They will hit other free electrons and get repelled in another direction. They constantly keep hitting other atoms or free electrons and move in random directions.

When we connect the conductor to two surfaces with opposite charges, they will experience a force down the line from negative to positive. Due to this force they will now move in a general direction from negative to positive but they will keep colliding with other atoms and electrons along the way.

This movement is called the drift velocity of the electrons. When we zoom out it feels that the electrons are drifting from the negative side to the positive side. Hence we say that an electric current is flowing down the wire. Although they move very slow their effect moves a lot faster (near the speed of light).

Lets understand this with an analogy. Imagine a long queue of people waiting to get into a sports stadium. The queue is moving very slow and every person is a bit agitated. The last person cannot control his agitation and pushes the person in front of him. The person being pushed in turn pushes the person in front and it goes on until it reaches the first person. Here the last person is still at the end of the queue and moving very slow but the effects of his agitation have reached the other end very fast.

Electrons and heat

We have seen that electrons constantly collide with other electrons and atoms in a conductor. This collision generates heat. The faster the current the more heat it will generate. Hence a lightning strike generates a tremendous amount of heat.

When we heat a conductor the atoms start jiggling more and will increase the neighbouring atoms jiggle. This is how they conduct heat. This jiggling however provides resistance to the free electrons and they cannot wriggle through. This means that the conductivity of the conductor decreases when heated and it should increase when cooled.

Electronics

It is interesting to learn how electrons behave. We have just scratched the surface but without getting into complex physics, mathematics and chemistry we have learnt a lot.

The field of electronics deals with using electrons to do work (Get the relation? “electron-ics”). It brings light to our homes and moves the fan in the hot summer.

We will use most of our understanding here to master the fundamentals of electronics in future posts.