







GCSE science Coursework An investigation into the relationship: V= I. R September 2003 By Helen Crutcher Bibliography The objective of the examination The goal of this examination is to see what the relationship in between voltage, current and resistance is. We will be performing two various experiments examine Ohms law, V= I. R using, in our very first experiment wire density as our input variable. In our 2nd experiment, we will use wire length. In each, we will tape the Voltage and existing running through the circuit and use this details to exercise wire resistance.
Background information Voltage: Voltage is Present: Current is Resistance: Resistance is a procedure of how much the present in a circuit is slowed down. Resistance is triggered when electrons have to’ jump’ from one It is determined in Ohms (?) Ohms law Electrons Introduction Hypothesis the thicker or shorter the wire the easier it is for existing to flow round the circuit so more existing flows through the circuit therefore the smaller sized the resistance (R = I.
V) I have developed this hypothesis because of my understanding of the circulation of electric current through a circuit.
As seen in my background details I predict that if I plot a chart of Resistance versus wire thickness for my results I will get a graph similar to the one bellow A table to show which variables we will require to control in order For this to be a fair test and which ones we will measure: Experiment one: wire density Experiment 2: wire length Input variable Control variables – for a fair test Outcome variable Variable Variety interval Variable Value Variable Wire density 0. mm 2. mm Length of wire 10cms Present Setting of resistor Constant Kind of wire
Nickel Chrome Supply Voltage Input variable Control variables – for a reasonable test Result variable Variable Range period Variable Worth Variable Wire length 4cms Width of wire Present Setting of resistor Consistent Kind of wire Nickel Chrome Supply voltage Initial experiment Doing an initial experiment is needed when doing any investigation due to the fact that it permits us to strategy which variables and ranges will appropriate for usage, for our real experiment to offer us reputable outcomes. Approach for initial Preliminary results Experiment one Wire thickness.
Voltage Current Resistance The gradient of this graph represents mass, so this shallow gradient shows that the mass must be large. Evaluation of preliminary experiment Our preliminary experiment shows us that we will be able to use this range of values for our final experiment since they gave us results that were relatively consistent with our hypothesis. Equipment needed: Different lengths of Nickel Chrome (nichrome) wire(experiment two) Different widths of ! 0 cm long Nichrome wire (experiment one) .
Ammeter Variable resistor Voltmeter Power pack wires Crocodile clips Pulley Method for final experiment A table of results from the experiment: Processing results Preliminary results Actual results Analysis Conclusion: Our findings do appear to have followed what we said in our hypothesis and seem to show the relationship that we predicted, but more experimentation is needed to prove conclusively. We can definitely see, from our graph that the relationship between wire length and Resistance is, as we said a positive, proportional one, as the wire length increases, the resistance increases.
This relationship shows a relatively proportional graph because when you increase the length of the wire there are more atoms in the wire, this means than in order for electrons to flow they must pass between these atoms, the fewer atoms the electrons jump between the less opposition there is to them in the circuit. What’s more, they bump into each other less, and so don’t create friction and loose their energy as heat. If the electrons are loosing less of their energy then the resistance for a particular voltage must change ( V=I.R) and must get smaller because there is a bigger current to go into the equation.
The conclusion reasonably supports the prediction because all of the results that we collected follow the pattern we expected. Analysis Evaluation ResistanceResistance is measured in Ohms (symbol ? ). Resistance The bigger the resistance, the smaller the current. The very important equation V = I x R is an expression of Ohm’s Law. You MUST KNOW this equation for the exam! If the resistance of a component is constant (stays the same) for different values of V and I, then a plot (graph) of V against I will be a straight line.
The gradient (slope) of the line shows how big the resistance is. A test circuit is used to find a range of voltages and currents for a component. Components which obey Ohm’s Law are Wires and Resistors. A component will only obey Ohm’s Law at constant temperature (meaning that the temperature must not change). In reality, an increase in current through a component will change its temperature (the temperature usually goes up), and so Ohm’s Law is only an approximation but it works quite well for many components. The next page shows plots for components which don’t obey Ohm’s Law.
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