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How does the length of a piece of Nachrome wire affect its electrical resistance.

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Introduction

How does the length of a piece of Nachrome wire affect its electrical resistance. AIM: To investigate how the electrical resistance of a wire changes in relationship to its length. DEFINITION OF RESISTANCE: Electrons move more easily through some conductors than other when a p.d is applied. The opposition of a conductor to current is called its resistance. A good conductor has a low resistance and a poor conductor has a high resistance. The resistance of a wire of a certain material. * Increases as its length increases * Increases as its cross-sectional area decreases * Depends on the material. FACTORS AFFECTING THE RESISTANCE OF A WIRE: Factor How does this affect the resistance? Length of the wire If you double the length of the wire this doubles the resistance, since twice the length of wire is equivalent to two equal resistances in series. The resistance of a wire is therefore proportional to its length. Thickness of the wire Thick wires are equivalent to a number of thinner wires of equal area joined in parallel. The resistance of a wire is inversely proportional to its area of cross-section. ...read more.

Middle

VARIABLES: When doing any experiment it is always important to only have one variable and to keep all the other readings constant, this provides a fair test. In this experiment I will have one variable, this will be the length of the Nichrome wire. The following variables will remain constant to make a fair test: The room temperature. If we do not keep the room temperature the same the particles will move faster and this will affect the resistance. To make sure that there is no electrical heating in the wire I will keep the current low. The cross sectional area of the wire must be kept the same. The resistance of the wire is inversely proportional to its area of cross-section. The material under test. The material of which the wire is composed is another important factor to be considered when deciding the length and gauge of wire for a particular resistance. The current. If this is changed the temperature of the wire would change and this would provide extra resistance. I will control the current using a variable resistor. I will make sure that there is a small voltage and a high resistance; this will keep the temperature of the wires down. ...read more.

Conclusion

Shocks from wires Turn of power supply before touching the circuit set up. Cutting wires. Always be careful when cutting wires. DIAGRAM FOR MAIN EXPERIMENT: The power supply will be kept at a constant three volts. The voltammeter will have a range from 0-5 V The ammeter will have a range of 0-10 Amps to the nearest 0.1 of an amp. The variable resistor will be a component in the circuit to allow me to keep the resistance up so that the wires do not heat up from high currents. METHOD: Set up the experiment as shown in the diagram. From my main experiment I will fill in the following table: Length of wire (cm) Voltage 1 (V) 2 Average Current 1 (A) 2 Average Resistance R = V / I (Ohms) 10 20 30 40 50 60 70 80 90 100 The length of the wire will be measured to the nearest mm. The voltage will be measured to 0.1 of a volt. The current will be measured to 0.1 of an amp. I will take three readings at each measurement; this will allow me to take an accurate average that will allow me to draw an accurate graph. PREDICTED GRAPH FOR MAIN EXPERIMENT: ?? ?? ?? ?? ...read more.

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