Wire The Resistance example essay topic

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, 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. Nichrome 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 nick rome 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 4 V. 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 10 mm, I will measure the current going through the wire and then I will measure the voltage across the 10 mm of wire. 8.

I will then find the resistance of the wire using Ohm's Law, where I will have to divide the obtained voltage by the current reading to get the resistance. 9. I will repeat the above process for all the lengths of wire, ranging from 100 mm to 500 mm. 10. I will repeat the entire experiment three times to make sure all results are accurate. 11.

Because I will have three measurements for the resistance of each length of wire, I will find the average of these two readings. Safety: I need to keep the wire cool to avoid burns and accidents. We do this by making sure that the voltage we use doesn't get to high and so the current doesn't get too high. I will keep water away from the experiment and not touch the wire. From the graph we can see that the longer the length of wire the higher the resistance is, which is exactly what I predicted. If I take the resistance at 200 mm then we see that it is 0.83 ohms, if I double the length to 400 mm then the Resistance increases to 1.70.

This increase an increase of nearly exactly double which is what I predicted in my prediction. If I take the gradient of this line of best fit then I can calculate the increase in Resistance every mm. This gives me a value of: Change in y = 3.00 - 0.84 = 2.16 Change in x = 700-200 = 500 Gradient = 2.16 / 500 = 0.0043 ohms per mm This proves that every mm you go along the wire the resistance increases by 0.0043 ohms. This is due to the extra collisions that the electrons have with the metal ions. Evaluation: Overall I think my experiment was done quite efficiently.

According to my graph my first result was slightly anomalous. This may have been because this was my first reading and was therefore maybe slightly cooler or.