Lab Report: Testing How the Length of a Wire Determines its Resistance :: essays research papers

Science Coursework The Resistance of a Wire Aim: To find out how the length of a wire affects the resistance of it. Knowledge: Ohms Law is a mathematical equation that shows the relationship between Voltage, Current and Resistance in an electrical circuit. It is stated as: , V = I x R , R = V / I , I = V / R Where  · V = Voltage  · I = Current (I stands for INTENSITY)  · R = Resistance In order to understand what Ohms Law is all about you need to understand electricity and what makes Voltage, Current and Resistance in a circuit. Current Current is the movement of electrons in a circuit but "What are electrons and what makes them move?" All matter is made up of Atoms. Piece of metal made up of Atoms Each atom is made up of a nucleus that has a certain number of protons and neutrons with an equal numbers of electrons in orbit. The copper atom has 29 protons in its nucleus with 29 electrons orbiting the nucleus. The electrons are arranged in orbits called shells. Notice that in the copper atom, the outside shell has only one electron. The outer shell of any atom is called the valence shell. When the valence electron in any atom gains sufficient energy from some outside force, it can break away from the parent atom and become what is called a free electron. It is very easy to provide enough energy to cause the valence electron to become free. Some sources of energy are heat, light, magnetic fields and a voltage source. When the valence electron becomes free it leaves behind an atom that has a positive charge. Remember that the copper atom has 29 + protons and 29 electrons so if one electron leaves orbit we are left with +29 protons and 28 electrons. That means the atom has a more positive charge because of the one less electron. This is an unbalanced atom and is not natural. The atom will always try to get an electron back into the valence orbit to become normal or balanced again. This is the one fact that you should remember and try to visualize when working with electrical circuits. Electric current is the movement of electrons from one atom to another in a conductor. If you can visualize a piece of copper wire with billions of atoms and each one of them losing an electron and all the electrons jumping to other atoms, you will begin to see what current is.