We are investigating how the current flow through a wire, which is part of an electrical circuit, can be altered. In doing this the resistance of the wire will be measured. It’s an extension of earlier GCSE work using cells, lamps, ammeter, voltmeter and variable resistors. There are two types of circuits, series and parallel. In class experiments we found out that for: Series circuits- more lamps in series, the lamps become dimmer and the current flow through them becomes less. Parallel circuits- more lamps in parallel, the lamps remain equally bright and the total current splits equally between each branch of the circuit.
Something has happened to the resistance in each type of circuit. Series circuit = More lamps = More resistance = Less current. Parallel circuit =More lamps = More current = Less resistance. This is because as the resistance of the lamp increases, the temperature of the filament wire also increases; therefore the particles in the wire vibrate more and make it harder for the electrons to pass through. Background Information The and materials I have used are: Class notes AQA GCSE science CGP GCSE physics Prediction My prediction for this investigation is that the larger the cross sectional area, the more current can flow through it.
The more times the electrons will collide. Increasing the length of the wire will result in double the resistance. This is because by increasing the length of the wire it is also increasing the collisions that will occur. Justification A current flow in a wire is a flow of electrons, provided by energy, maybe from a cell or battery. The resistance restricts the current flow and if there is more resistance there is less current. 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 formula:
R=V/I Where V = Voltage, I = Current and R = Resistance Electricity is conducted through a conductor, in this case wire, by means of electrons. The number of electrons depends on the material and more electrons means a better conductor, i. e. it has less resistance. The electrons are given energy and as a result move and collide with neighbouring electrons. This happens across the length of the wire and electricity is conducted. Resistance is the result of energy loss as heat. It involves collisions between the electrons and the fixed particles of the metal, other electrons and impurities.
These collisions convert some of the energy that the electrons are carrying into heat. For example, if there is water pipe where the water is the electricity, the water is the electric current and the pump is the battery. In the water pipe there is a part where the pipe is narrow less water will be able to get through that part of the pipe. So the water is restricted and this is exactly the same as the wire where the resistance will restrict the current. Plan Before we started our experiment we did some preliminary work in order to find a safe current to work at, because resistance is temperature dependant. Equipment list:
Power Supply Potential Divider Ammeter Voltmeter Set of Wires Wire (testing wire) Ruler 1) Arrange apparatus as shown in the Diagram. 2) Attach the wire to the crocodile-clips. 3) Attach the wire at 10cm, 20cm, 30cm, 40cm, 50cm, 60cm, 70cm, 80cm, 90cm, and 100cm. 4) Set the current using the variable resistor to the currents required. 5) Take the reading from the voltmeter and record in results table. 6) Repeat 3 times for each length of wire. 7) Then work out the resistance using the formula Vi?? I=R (Voltage i?? Current = Resistance) 8) Do the same for different type of wires and plot on a graph.