8. Ammeter (The equipment used to measure the voltage) 9. Voltmeter 10. Digital multi-meter 11. Material of wire 12. Cross section of wire These factors if not controlled can affect the experiment and give me false data. The other factors must be controlled to make sure that I am measuring the affects of the correct (input variable) that I have chosen, (in this case the resistance of resistor 1. ) These factors are known as the control variables and they give you something to compare your results with, (and make your experiment repeatable, as you will have kept the conditions for your experiment the same.
) The output variable is the variable that will change due to the input variable in this case the Voltage out. (The other factors are mainly kept the same for accuracy. ) In my experiment I will be using a potential divider circuit (A circuit diagram of two fixed resistors in series. They can be used to split the voltage of a circuit) to find out how changing the resistance of Resistor 1 affects the total output voltage of a potential divider circuit. I will take all possible variables into consideration and I will try to make this experiment one which will create reliable and as accurate results.
The experiment will be carried out in the school science lab where I will record the results and then conclude my experiment to prove whether my hypothesis correct or false. I predict that, when the resistance for Resistor 1 is increased the voltage out (Vout) will decrease. I know this because, the more atoms and electrons there are in a wire, the harder it is for the electrons (the current) to get past the atoms (the resistance) and around the circuit to the positive end. Diagram of an atom The nucleus of an atom consists of neutrons (neutral) and protons (positively charged), which are in a fixed stationary position.
The electrons (negatively charged) on the outer shells however can move freely at high speeds. What is current? A metal wire is made of metal atoms; most metal atoms have one or two electrons in their outer energy level. When there is no conducted electricity present, the electrons will and can move freely in any direction. (Diagram of a metal compound, electrons moving freely, purple: electrons. Green: atoms) Delocalised electrons are spread across more than one atom. Electrons in materials are usually bound to one atom. Atoms are held together by the interactions of the charges on different atoms.
In some cases, electrons can be shared between atoms, and are then called delocalised. The electrons will randomly move around the whole molecule structure and we end up with a regular lattice of metal atoms in a sea of negatively charged electrons. When electricity is introduced however the negatively charged electrons will instantly begin to move through the wire in the same direction (towards the positively charged end) this is an electric current, a current is the flow of charge in a wire or the movement of the negatively charged electrons through the wire.
The electrons move like this because of the voltage (energy/ power) which pushes the current around the circuit. The energy is transferred from the power pack to the electrons that will equally share and give out the energy to each component in the circuit. By the time the electron has reached the end of the circuit it will have lost all the energy it will have in gained at the start (energy will be lost through components and resistance. ) Resistance is the opposition that the electrons will experience while flowing through the wire.
An electron travelling through the wires encounters resistance. An electron does not travel in a direct route; instead it adopts a zigzag path due to the countless collisions with the atoms in the conducting material. When electrons move against the resistance, friction is generated. The friction produced by electrons flowing against the resistance will cause the wire to heat. (The hotter the wire, the higher the resistance. ) Resistance depends on the material, cross section and length. Resistance limits the amount of current flowing through the circuit for a given voltage of the power supply.
For a circuit to work there must be no breaks, if there is a break then everything stops. An electric charge must also go all the way round the circuit. When a wire heats up they will act differently and a blockage will be made. This is a sign of Resistance. I have chosen to keep the voltage at 12 volts as this is the highest number of volts possible on the power pack. Using a higher voltage In, means that I will get higher results for Vout. I will also be able to record them in numbers that are easy to handle and work with, and a more significant range.
Even though I have chosen my voltage to stay at stay 12 volts due to the power packs being not completely accurate, the voltage In will, change because I will be purposefully changing the resistance of the circuit. Everything in a circuit is not mutually exclusive; when one factor is changed every other factor will also change, as they are all interlinked and dependent on each other. As I know that the Voltage In will change, I will make sure that every time I test the resistance of the circuit I will also check the voltage of the circuit and record the result for that down too.