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Investigate the resistance of a wire and the factors affecting it.

Extracts from this document...

Introduction

Resistance investigation.

Task:

The purpose of this investigation is to investigate the resistance of a wire and the factors affecting it.  

Introduction:

Resistance is a force which opposes the flow of an electric current around a circuit so that energy is required to push the charged particles around the circuit. The circuit itself can resist the flow of particles if the wires are either very thin or very long. e.g. The filament across an electric bulb is quite thin as needs to resist the flow of particles for the bulb to glow.
Resistance is measured in ohms.

George Ohm discovered that the emf (electromotive force) of a circuit is directly proportional to the current flowing through the circuit. This means that if you triple one, you triple the other. He also discovered that a circuit sometimes resists the flow of electricity. He called this resistance. He then came up with a rule for working out the resistance of a circuit:


V/I = R
image00.png

V - Volts
I - Current
R - Resistance.

There are three main things that resistance depends on:

  • The length/width of the wire used.
  • The temperature of the wire.
  • The type of metal used for the wire.

Water analogy:

...read more.

Middle



My graph should show that the length is directly proportional to the resistance.

Predicted graph:

image02.png


Variables:

When measuring resistance in a length of a wire, the independent variable is the length of the wire and the dependant variable is the resistance.

There are 6 key factors that affect resistance:

∙        The metal used.  Some metals have a lower resistivity than others, which allows them to conduct more electricity. If the resistivity is lower, the resistance is lower.

∙   The width of the conductor. Wider conductors allow more electrons to flow through them.  The wider the conductor is, the lower its resistance.

∙   The length of the conductor. This affects the resistance because the electrons have a longer journey, which needs more energy to complete. Shorter materials have less resistance as opposed to longer materials.

   The temperature of the conductor. Metals conduct better at lower temperatures, although there           are a few exceptions to this rule, this is because the molecules are not moving and are next to   each other to allow easy conduction of electrons.

∙   The amount of energy being given off as heat. Built up energy is given off as heat, as a metal conducts electricity. As electricity is lost more heat is being given out.

...read more.

Conclusion



Temperature :

I think that if the wire is heated up the atoms in the wire will start to vibrate because of their increase in energy. This causes more collisions between the electrons and the atoms as the atoms are moving into the path of the electrons. This increase in collisions means that there will be an increase in resistance.

Material :

I think that the type of material of the wire will affect the amount of free electrons, which are able to flow through that wire. This is because the number of electrons depends on the amount of electrons in the outer energy shell of the atoms, so if there are more or larger atoms then there must be more electrons available. If the material has a high number of atoms there will be high numbers of electrons causing a lower resistance because of the increase in the number of electrons. Also if the atoms in the material are closely packed then the electrons will have more frequent collisions and the resistance will increase.

A more accurate way to determine the resistance of the wire is a multimeter. A multimeter is a device that can measure the resistance of a material, cutting out the separate voltmeter and ammeter. This method would increase the accuracy of the meters, for one meter has a lot less interference than two, thereby increasing the accuracy of the results.

...read more.

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