Investigating How The Length Of A Wire Affects Its Resistance (The factors in this investigation are: (The material used for the wire, as some materials are better conductors of electricity than others so more electrons will pass through good conductors. (Cross-sectional area as the thickness of the wire increases the resistance decreases, for example if the wire is thicker more electrons will be able to pass through and if the wire is thinner fewer electrons will be able to pass through, thus a higher resistance.
(Length of the wire as the length increases the resistance increases this is because the electrons have further to travel thus there is more resistance. (Temperature of the wire as the temperature increases the resistance decreases, for example if the wire is hot there will be a lower resistance and if cold there will be a higher resistance. I am going to investigate whether changing the length of a wire affects the resistance (of the wire). Planning: (The independent variable I have chosen to change is the length of the wire.
(The controlled variables are the materials used for the wire, the cross-sectional area and the temperature of the wire. (The dependant variables are the potential difference and current. (I will work safely by using equipment properly by putting equipment away after use and by handling the electrical equipment and the sharp, thin wires carefully. Therefore the equipment is kept well away form the edge of the bench and that the electrical equipment is well supervised. (I will make sure that scrap pieces of wire are thrown away after use.
(I will make sure that the electrical equipment is kept well away from liquids and solutions, such as water in nearby taps. (I will make sure that I am aware of the sharp, thin edges on the wires so I do not cut myself. (I will keep my hair tied back so that it does not interfere with the experiments by coming into contact with my electrical equipment. (I will make sure that all of the electrical equipment is properly inserted into the electrical sockets and power packs. (I will make sure that I will not drop any dangerous equipment onto the floor, my hands and on other people also.
(I will make sure I always turn off the power pack before changing the length of the wire. (I will make sure the current is not high or the wire will over heat. (I will also make sure that there is a low voltage so I do not get an electric shock. (To make it a fair test I will use the same type of wire: 32 swg, 0. 28 diameter, (Same ammeter, voltmeter, rheostat and the same types of other equipment to be used in the tests, (Same current flowing through the circuit: 2 V starting from the power pack, (That the rheostat is set at a constant resistance to control the current: 0. 5 amps,
(To measure the current, voltage and the lengths of the wire accurately to two decimal places. (The apparatus that I will use is: (A power pack, (Wires, (A metre ruler stick, (Wire cutters, (Plastic tape/ Masking tape, (A rheostat is set at a constant resistance to control the current. (An ammeter is used to measure this control. (And a voltmeter to measure electrical force. (During the experiment I will firstly put measured lengths of copper wire, which are attached to electrical wires in a series circuit at both ends. In the circuit there will be a rheostat, voltmeter and an ammeter.
The rheostat is there to control the current and an ammeter to measure this control. The voltmeter is there to measure the electromotive force (emf), which is the push/energy in the circuit. I will alter the lengths of the wire by attaching the copper wire to a metre ruler stick and adjust the other wires so that they are attached at the different lengths specified. I will then record my results in a table to two decimal places (the voltage and amps). I will then find the averages of the voltage and use them to find the resistance of the different lengths of the wire using Ohm’s Law.
(To measure the resistance you cannot measure it directly so you have to measure the current (the number of electrons) with an ammeter in a series circuit, which is measured in amps/A and has a low resistance. I will also have to record the voltage with a voltmeter in a parallel circuit, which is measured in volts/V and has a high resistance. With these results I will then have to use Ohm’s Law to calculate the resistance, which is: (Ohm’s Law: Resistance= Voltage Current (Diagram of equipment: Power pack Voltmeter Ammeter Copper Wire Wires (32 swg, 0. 28 mm Diameter) Rheostat.
(A diagram to show what equipment I have chosen to use to perform my experiment. Also to show how I will use my equipment. (I will increase the length of the copper wire by 100 millimetres each time, so I will start at zero and increase the length up to 1000 millimetres. I will start at zero (0 millimetres) because it is a good control to show no change and accuracy. (The range of lengths of wire I have chosen are: (0 mm, (100 mm, (200 mm, (300 mm, (400 mm, (500 mm, (600 mm, (700 mm, (800 mm, (900 mm, (1000 mm. (These lengths were chosen because I wanted to see if the time would affect the resistance of the wire.
(This is a sufficient length span to identify the (line of best fit) trend of this experiment portrays so it will help conduct an accurate line of best fit on a graph. (I will be doing six tests (with eleven different lengths of wire). Therefore I will be doing the whole experiment more than once through to reduce human error. This is because I want to find overall averages and to try to make the experiment as accurate as possible! (I predict that as the length of the wire increases the resistance of the wire will increase.
I will also expect that the line of best fit will be proportional after finding the resistance of the different lengths of the wires. (`Georg Simon Ohm (1787-1854) A German physicist, best known for his research on electrical currents. His formulation of the relationship between current, electromotive force and resistance, known as Ohm’s Law, is the basic law of current flow. The unit of electrical resistance was named the Ohm in his honour. ‘ This information was needed so I would be able to understand how and why it is called Ohm’s Law and who invented it.
(`Ohm’s Law ExplainedThe amount of current flowing in a circuit made up of pure resistance’s is directly proportional to the electromotive forces impressed on the circuit and inversely proportional to the total resistance of the circuit. In simpler terms, Ohm’s aw means: 1. A steady increase in voltage, in a circuit with a constant resistance, produces a constant linear rise in current. ‘ Ohm established that by increasing the voltage with a constant resistance produced a rise in current and also I know that using different materials for wires creates different gradients of slope. 2.
`A steady increase in resistance, in a circuit with constant voltage, produces a progressively (not a straight line if graphed) weaker current. ‘ He also established that by increasing the resistance with a constant voltage produced a progressive rise in current, as the temperature of the wire increased. This is why I kept a constant current at 0. 5 amps. From these graphs Ohm derived the law he invented below. `In electricity, experimentally discovered relationship that the amount of steady current through a large number of materials is directly proportional to the potential difference, or voltage across the materials.
Ohm’s Law as a formulation of the relationship of voltage, current and resistance, expressed as: V= I X R Or I= V R R= V I Where: V is the voltage measured in volts (V). I is the current measured in amperes (A). R is the resistance measured in (? ). Therefore: VOLTS = AMPS X RESISTANCE’ I used Ohm’s Law to find the missing value, which was the resistance. (`Electrons Voltage: Batteries and generators all push out electrons. The higher the voltage, the harder they push. Voltage is the electrical force, or ‘pressure’, that causes current to flow in a circuit. It is measured in Volts (V).