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Resistance Coursework

Essay by   •  November 8, 2010  •  Essay  •  1,018 Words (5 Pages)  •  1,109 Views

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Resistance coursework

Aim: My aim is to find out which factors affect the resistance of wire and how they affect them.

Ohm's Law:

Ohm's law 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 Ñ' 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.

Resistance is the ratio of Voltage : Current and we calculate it by using the equation R=V/I.

Variables:

 Material of wire: In my experiment I will be using wire, because it has a high resistance. This could be either it has a closer ions or more ions than other metals. For example Copper has a low resistance due to the arrangement of its ions.

 Temperature: A rise in temperature causes ions inside the metal to vibrate more causing electrons to collide into them this builds resistance; therefore the electrons find it harder to get through the wire. The greater the temperature the greater the resistance because electrons are colliding more causing friction. Therefore the relationship between them is directly proportional.

 Cross section of the wire: The thicker the wire the easier it is for the electrons to go past. The thinner the wire, the smaller the area the electrons have to pass through. This means that they collide more often and as a result sacrifice more of their energy to the neighbouring particles in the wire. The cross section of the wire and the resistance is inversely proportional this means that the greater the thickness of the wire the lower the resistance.

 Length: The longer the wire the more ions there are for the electrons to get past. Energy has to be used to push current through a wire. If the electrons have to travel further in a long wire, therefore more energy will be needed. The relationship between resistance and the length of the wire is directly proportional this means that the greater the length of a wire the larger the resistance.

My chosen variable:

The variable I have decided to use is the length of wire because I believe that it is the easiest to control to my ability.

Prediction:

I predict that as the length of the wire increase so does the resistance. This is due to the idea of the free moving electrons being resisted by the atoms in the wire.

Equipment:

In my experiment I will be using the following equipment:

 Power Pack: To supply the potential difference.

 Ammeter: To measure the current.

 Voltmeter: To measure the potential difference.

 Nicrome wires: To be used as a conductor.

 6 Connecting wires: To complete the circuit.

 Variable Resistor: To make sure we have a constant current in order to take an average measurement.

Method

1. I will measure the resistance of 8 different lengths of nickrome wire using a tape measure.

2. I shall join the multimeter in series with a Direct current power supply (i.e. a power pack), setting the value to 4V. The multimeter is better to use because of the larger currents and because the readings are given to 2 decimal places.

3. I shall then proceed to connect a 50 mm length of nickel-chrome wire, which shall be measured using a tape measure, he output from the ammeter.

4. I shall then connect the voltmeter across the wire I will be testing.

5. Then I will attach the negative terminal of the voltmeter to the negative terminal of the power supply, therefore completing the circuit.

6. 100 mm of wire were stepped off by the voltmeter leads and I recorded the readings of voltage and current

7. For the first length, which will be 10mm, I will measure the current going through the wire and then I will measure the voltage across

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