5098 words - 20 pages

Aim: - In this experiment I will be finding out the resistance of a wire in which its length is the variable. I will be investigating the process of how much the resistance changes due to the increase of the length of the wire (constant wire).Electrical CurrentElectric current is the rate of charge flow past a given point in all electric circuit, measured in coulombs/seconds, which is named amperes. In most DC electric circuits, it can be assumed that the resistance to current flow is constant so that the current in the circuit is related to voltage and resistance by Ohm's law.I = V/RThe unit of electric charge is the coulomb. Ordinary matter is made up of atoms which have positively charged nuclei and negatively charged electrons surrounding them. Charge is made as a multiple of the electron or proton charge.Also the rate flow of electric charge is called electric current and is measured in amperes.BasicsIn a conductor, electric current can flow freely and in an insulator it can't. Metals such as copper are good conductors while most non-metallic solids are good insulators having very high resistance to the flow of charge through them.Conductor implies that the outer electrons of the atoms are loosely bound and free to move through the material. Most atoms hold on to their electrons tightly and are insulators. In copper, the outer electrons are essentially free and strongly repel each other.Cross-section of copper wire:VoltageVoltage is a measure of the amount of 'push' given to electric charge in a circuit. If there is no 'push' electrons will not be moved around the circuit. This voltage would normally be supplied by a cell battery or power pack.Voltage and energy are linked the more you push an electron, the more energy it will be given.1 volt is the voltage that gives 1 coulomb of charge energy of 1 joule (J).The equation describing this relationship is:Voltage = energy/chargeThe two rearrangements of this equation will therefore be:Energy = voltage x charge (Q = E/V)ResistanceResistance is a force, which opposes the flow of an electric current around a circuit so that the energy is required to push the charged particles around the circuit. The circuit itself can resist the flow of particles if the wires are either very thin or very long. Resistance is measured in Ohms.George Ohm discovered that the voltage of a circuit is directly proportional to the current flowing through the circuit. This means that if you triple one, you triple one, you triple the other. He also discovered that a circuit sometimes resists the flow of electricity. He called this resistance. He then came up with a rule for working out the resistance of a circuit.Resistance () = Voltage (V) / Current (A)Also the temperature can determine the resistance of the resistor. It's not just the resistor that causes resistance in the circuit, as any component in the circuit causes resistance. The 4 variables for the experiment are the length, diameter of the wire, the material the...

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