The aim of this investigation that I am about to embark on is to research into the resistivity of a wire found on an ancient mummified Persian princess who according to one translation is a daughter of the King Xerxes which was about 2,600 years ago. After I have found the resistivity of this wire, I will compare and contrast it with other resistivities of the different types of contemporary wires available today in order to interpret and conclude whether it is made from a modern alloy. Theory An electric current in a wire is the passage of moving charge through the material.
Charge is carried by particles such as electrons and ions. In some materials such as a metal, the charge is carried by electrons. In other materials such as salt solution, the charge is carried out by ions. If charged particles are moving, a current is produced. Electrons moving in a circuit are negatively charged. They move from the negative terminal to the positive one. In spite of this, the direction of the current in a circuit is taken as being from positive to negative. A current in a wire is due to the movement of free electrons.
A wire consists of millions of atoms which have electrons tightly bounded to the atomic radius by the electrical attractive force between the positive nucleus and the negative electrons. In solids, one or two of the outer electrons surrounding each atom are used to form the bonds between atoms that hold the solid itself together. In a metal, these bonding electrons are free to move through the entire solid which is often referred to as “free electrons”. The unit of charge is (C) and the unit of current is ampere or amp (A). If an amount of charge ? Q flows part a point in a time interval ?
t, then the equation of current is: Current (I) = charge (? Q) i?? time interval (t) Charge neither created nor destroyed (it is conserved) and there is no build up of charge anywhere in a circuit, so the rate at which charge flows towards any point in the circuit must be the same as the rate at which it flows away. Energy transfers in electric circuits are often expressed in terms of energy per unit charge. The unit of energy is Joule (J) and the unit per unit charge is volt (V)= I J C-1. This is usually called potential difference (pd) or voltage. The equation of voltage in a circuit is expressed as:
V= W Q The emf of a power supply is a measure of the total energy that it supplies to each coulomb of charge. Energy cannot be created nor destroyed but conserved instead. Therefore the energy transferred to the components in a circuit is required to be equal to the energy from the power supply. In the time that it takes for one coulomb to pass through any point in the circuit, the energy transferred by the power supply is mathematically equal to its emf. So the sum of all the “pds” across all the components in a series circuit is equal to the emf of the power supply.
When the components in the circuit are connected in parallel, each has the same potential difference across it. When a metallic wire is placed in an electric circuit, the voltage from the battery makes the electrons flow through the wire. As they do so, they collide with the metal ions in the wire and this process slows down the gradual continuous flow of the electrons. This is called Resistance. It is defined as the electrical property of a material that makes the moving charges dissipate energy. The resistance (? ) of a conductor is classified by the equation: R = V I Factors That Affect Resistance.
Temperature is one of the main factors that affect the resistance of a wire. If a metal is heated, the metal ions in it will vibrate more. This means that there is a greater chance of an electron bumping into a metal ion so the flow of electrons is reduced (i. e. the resistance is increased). An analogy of this theory is to imagine an individual walking through a crowd of people (who in this case are metal ions and the individual the electron). If the crowd are standing still (similar to soldiers on parade), the individual can easily move through by walking along the lines between the soldiers.