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Aim: Investigate how the length of a wire affects the current and resistance of a wire. Predictions The longer the wire, the higher the resistance. This is because the longer the wire, the more times the free electrons will collide with the other atoms, the particles making up the metal, and any impurities in the metal. Therefore, more energy is going to be lost in these collisions (as heat). Furthermore, doubling the length of the wire will result in double the resistance. This is because by doubling the length of the wire one is also doubling the collisions that will occur, therefore doubling the amount of energy lost in these collisions and also the electrons have doubled the distance to travel Background information What is resistance? Resistance is a measure of how hard it is to move the electrons through the wire George Ohm discovered that Ohms law and how to measure resistance using a voltmeter and an ammeter. 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 (emf) impressed on the circuit and inversely proportional to the total resistance of the circuit. The law is usually expressed by the formula I = E/R, where I is the current in amperes, E is the electromotive force in volts, and R is the resistance in ohms. This enables us to work out the resistance using the current and Voltage. V/I = R V - Volts I - Current R - Resistance Scientific theory Electric current is the movement of electrons through a conductor. In this experiment a metal wire will be the conductor. When resistance is high, conductivity is low. Metals conduct electricity well because the atoms in them do not hold on to their electrons very well. Free electrons are created, which carry a negative charge, to 'jumpī along the lines of atoms in a wire which are in a lattice structure. Resistance is when these electrons which flow towards the positive collide with other atoms, they transfer some of their kinetic energy. This transfer on collision is what causes resistance. So, if we double the length of a wire, the number of atoms in the wire doubles. This increases the number of collisions and energy transferred twice, so twice the amount of energy is required. This means the resistance is doubled. Factors that affect resistance Temperature : If the wire is heated up the atoms in the wire will start to vibrate because of their increase in energy. This causes more collisions between the electrons and the atoms as he atoms are moving into the path of the electrons.
Approximate Word count = 1742
Approximate Pages = 7
(250 words per page double spaced)
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