In this coursework, I will be analyzing and proving that although metallic conductors are good conductors of electricity, they are affected by resistance. But there are factors affecting the resistance of a conductor, and through my experiments I am going to prove that. CONDUCTORS We know that there are two types of conductors of electricity. Good conductors and bad conductors. Good conductors are that which conduct electricity the best. There are also some conductors, called semi-conductors, since they only half conduct the electricity that is passed through them.
However, there are some materials, which resist the flow of electrons more that others do. These bad conductors are called insulators. Insulators are not needed to prove the factors affecting resistance, since they will be very invaluable, as they do not conduct electricity in the first place. When we talked about conductors conducting electricity, the very first question that comes up into our head is, ‘How do conductors conduct is electricity? ‘ In order to understand this, we have to learn about the structure of a metal, and to go deeper into it.
Every piece of metal is made of electrons in the shells around the nucleus, which contains the protons and neutrons. Thus the atom is stable when it has the same number of electrons and protons. But when we examine a piece of metal closely, we can see that they give out free electrons, to form a sea of electrons, and it is these electrons, that can carry the charges, thus conducting electricity. We know that for an object to be a good conductor of electricity, it has to be able to carry current charges, without much resistivity. Thus all metals are good conductors of electricity.
But some metals have more free electrons, so they are better conductors, since more electricity can be passed. EXISTENCE AND MOVEMENT We now come to our next question, ‘How does a wire conduct electricity? ‘ We all know now that the there are free electrons in any piece of metal, but it still can’t conduct electricity, if we just leave it by it self. This is because; there is no potential difference. If we examine a piece of metal closely, it turns out that the free electrons form a cloud, or a sea of electrons.
These electrons move randomly and haphazardly, thus, for e. g., in a copper atom, for every 5 electrons moving left, there are 5 electrons moving right, so the potential difference is nullified. And for a current to be present, there has to be a potential difference. Thus there is no charge in it. If we take the path of a single electron, it moves like the dust molecule in Brownian motion. But then anyone will ask, ‘ where do they get their energy from, if there is no battery connected? ‘ well this is due to thermal agitation, where electrons, take heat from the air, even if it is at room temperature, and there is no heat that we feel.
In addition, this thermal agitation causes atoms too, to vibrate, and shake. CURRENTS We learnt earlier, that because of there being no potential difference, there is no charge, but when we connect a battery, or a alternative current generator, or in other words, an ac supply, to a piece of wire, the battery creates a potential/electrical difference, thus current is able to flow. This happens, since, the external potential difference, causes the electrons to move in one direction, thus is creates a potential difference, as shown in the diagram.
We can see that since, the electrons are repelled at the negative end, they go towards the positive end, and so uniformly travel from negative to positive. For e. g. if we open the window of a very cold classroom, the heat sweeps inside, to nullify the effect, due to the potential difference in the temperatures. Also if we place water at a higher altitude, the pressure is more; so the water moves down to nullify the effect, due to potential difference in pressure. Thus we see if a potential difference is created in a wire, the electrons, move, in order to nullify its effect.
How do we create a potential difference? By using a battery or generator, we can create a potential difference, which causes the electrons to move, thus conducting electricity. When we connect the wire to the positive and negative ends of a wire, we can see that there is a potential difference on the two sides, i. e. one is positively charged, and the other is negatively charged. Thus the electrons move from the negative end, to the positive end, in order that the effect of the introduced potential divider is nullified. Circuit Flow Of electrons + – Battery RESISTANCE.
However, the electrons do not just move easily, as though it was a 100m straight race. Instead, it is more like a 100m hurdles race, where they collide with the vibrating atoms. This is resistance. Resistance in general in electrons, is the obstruction, or collisions faced by the electron. In order to find out how, much resistance, there is, we use ohm’s law. Ohm’s law states that the amount of current flowing in a circuit made up of pure resistances is directly proportional to the electromotive force impressed on the circuit and inversely proportional to the total resistance of the circuit.