Plan: resistance in a wire. To do this

Plan: In my investigation I will be finding out necessary factors that affect resistance in a wire. To do this I will be looking at different lengths of wire, different thickness and different materials. The three materials we will be using are Copper, Nichrome and Constantin. In the investigation I will take three sets of the same results and at least 6 measurements of wire being resisted. This way I can work out an average and also plot a graph. Circuits: There are two types of circuits, parallel and series; in this instance we will be looking at the latter.

Equipment: Voltmeter. Ammeter. Power pack. Crocodile clips. Wire. Different types of wires Length of wire. Thickness. Material. Diagram: Power pack The arrows are showing the way the conventional current goes. The conventional current goes from negative to positive. The actual current goes from positive to negative but when someone came up with the idea of the way current flows, he/she got it wrong. Important Information: Triangle for Resistance: Resistance is measured in Ohms. (? ) Current is measured in Amps. (A) Potential difference is measured in Volts. (V)

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Charge is measured in Coloumbs. (Q) Energy is measured in Joules. (J) Fair test: We will make this a fair test by taking 3 sets of each individual result, we take the totals from these results and work out the average. This will give us a fair result because the first couple of readings could be a total fluke. We will also try and keep the room temperature constant, Classroom temperature is approximately 23? C. We will also have to keep the voltage at our chosen 2 volts. We chose two volts for a safety reason, this reason is because any higher and it would probably burn the wire.

Also the minimum length can be 30cm because if there is an accident and the switch nudges the volts up then a fire could start because there is very little resistance in the wire. Research: Resistance makes it hard for a current to flow in the circuit. Here are the 4 things that makes resistance vary. 1 As the length of the wire increases the resistance increases. 2. As the cross sectional area increases the resistance decreases. 3. The material the wire is made from makes a difference, e. g.

Copper allows electrons to flow easily through it, i.e. It is a good conductor. It therefore has a relatively small resistance compared to, say, Nichrome. This does not allow electrons to flow easily and consequently there is friction as the electrons pass from atom to atom. Friction produces heat which makes the atoms vibrate more. Nichrome wire is able to give out lots of heat as the friction becomes more intense and that is why it is used in the heating element of electric fires. 4. As the temperature increases the resistance of a wire increases.

Ohm’s Law: A physical principle stating that the electric current flowing through a metallic conductor is directly proportional to the potential difference between its ends, as long as the temperature stays the same. The law is named after the German physicist who discovered the relationship in 1827, George Ohm. According to Ohm’s law, as the potential difference is increased a greater current flows. However, some materials put up more resistance to the flow of current than others, which is important in designing electrical equipment.

Preliminary work: In preliminary stages I carried out short experiments using two extreme lengths of copper wire. They measured 90cm and 30 cm. I found out that the larger piece of copper wire created a larger resistance than the shorter piece. Prediction: Based on my research and scientific knowledge I predict that as the length increase the resistance of the wire will also increase so the length and resistance are linked together directly proportional to each other. We should know that a wire should resist the flow of electricity, so the longer it is the more resistance it shall have.