## In “resistance” to the “push” from the

In this investigation I am going to find out (through an experiment) how much resistance a piece of copper wire will produce when it is used in an electric circuit. Theory; Inside a piece of copper wire there are millions of fixed protons. Electrons are attracted by these protons. These protons may give away one, two or three of the electrons attracted to them as long as they will get some from somewhere else (another set of protons), to make up for them given away. However, whilst an electron is missing from a set of protons it makes a positive ion. In an electric circuit, the power source supplies a “push” of electrons through the wires.

The protons layout throughout the wire supplies a “resistance” to the “push” from the power source. This resistance does not allow as many positive ions to be made. To measure the resistance within my circuit I shall be using the formula R=V i?? I Significant factors; Length of wire; The length of the wire would affect the resistance due to the length of the protons the electrons would have to push through. This will make the time for positive ions to be used longer. Width of wire; The width of the wire would change the number of moving electrons that could pass through the wire at any time.

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This would change the number of positive ions that could be made at any time. Temperature of wire; The temperature of the wire would affect the resistance due to the energy inside the wire. Material of wire; The material of the wire would change the resistance due to the structure of the atoms inside the wire; this would alter how easily the electrons would pass through. What I will change; The variable that I am going to change is going to be the length of the wire because I think it will be the easiest to change with the apparatus I have available to me, and I think it will be the easiest to do with a fair test.

Prediction; 1) I predict that the longer the length of wire gets, the more resistance will be put on the flow of electrons throughout the circuit. 2) I also predict that if I double the length of the wire the resistance within the wire will also double. Resistance of a Wire From www. courseworkbank. co. uk Resistance of a Wire Resistance of a Wire Task To investigate how the resistance of a wire is affected by the length of the wire. Theory What is resistance? Electricity is conducted through a conductor, in this case wire, by means of free electrons.

The number of free electrons depends on the material and more free electrons means a better conductor, i. e. it has less resistance. For example, gold has more free electrons than iron and, as a result, it is a better conductor. The free electrons are given energy and as a result move and collide with neighbouring free electrons. This happens across the length of the wire and thus electricity is conducted. Resistance is the result of energy loss as heat. It involves collisions between the free electrons and the fixed particles of the metal, other free electrons and impurities.

These collisions convert some of the energy that the free electrons are carrying into heat. How is it measured? The resistance of a length of wire is calculated by measuring the current present in the circuit (in series) and the voltage across the wire (in parallel). These measurements are then applied to this formulatance This can be rearranged to: R = V I Ohm’s Law It is also relevant to know of Ohm’s Law, which states that the current through a metallic conductor (e. g. wire) at a constant temperature is proportional to the potential difference (voltage).

Therefore V i?? I is constant. This means that the resistance of a metallic conductor is constant providing that the temperature also remains constant. Furthermore, the resistance of a metal increases as its temperature increases. This is because at higher temperatures, the particles of the conductor are moving around more quickly, thus increasing the likelihood of collisions with the free electrons. Variables Input:  Length of wire.  Material of wire.  Width of wire Starting temperature of wire. Output: and thus the resistance of the wire. i??  Voltage across wire.

Current in circuit.  Temperature of wire. The variable marked with a will be varied, the other input variables will be kept constant. The output variable marked with a i?? will be measured. 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 other free electrons, 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, thus doubling the amount of energy lost in these collisions. Method The following circuit was constructed to perform the investigation: wire The two dots ( ) represent the crocodile clips that were placed at the ends of the required length of wire. 1. One metre length of 0. 4mm diameter “constantan” (a metal alloy) wire is fixed to a metre rule. 2. The first crocodile clip is clipped to the wire at the 0cm position on the metre rule. 3.