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Factors Affecting the Current Flowing

Extracts from this document...

Introduction

Factors Affecting the Current Flowing

Through A Metallic Conductor

Planning

An atom consists of a positively-charged nucleus with negatively-charged electrons moving around it. Charge is measured in Coulombs and the charge on an electron is 1.6 x 10-19C. Most atoms have an equal number of positive and negative charges; therefore the overall charge is zero. However, in some atoms it is easy to remove an electron, leaving an atom with an unbalanced number of positive charges. This is called a positive ion.

When a battery is connected across the ends of the metal, the free electrons move towards the positive terminal of the battery which produces an electric current. When a metal atom gives away a free electron which has a charge of 1.6 x 10-19C, it gains a positive charge. The free electrons move amongst the positive ions, whereas the positive ions can only vibrate about their fixed positions. The free electron is a current carrier; for an electric of 1 ampere, 1 coulomb of electric charge moves every second.

The Current in Amperes can be calculated using the following equation:

Q                                        Where Q = Electric Charge

I = ──                                                    I = Current

t                                              and t = Time

There are many factors that affect the amount of current flowing through a metallic conductor:

• Length of wire
• Thickness of wire
• Temperature of wire
• Voltage
• Material of wire

All solids are made up of atoms that constantly vibrate about their positions. The higher the temperature, the greater the vibration. Electric current is the flow of free electrons through the material. As the electrons move, they collide with the vibrating atoms, so their movement is hampered.

Middle

0.093

I found that the problem with these results were the fact that the current was too high and I feel the reason for this was that the voltage, at 1.20V was too high. However I had a problem, 1.20V was the only voltage I could find where I could get a current reading for both extremes. The only way I could think of, of reducing the voltage was to add in another variable resistor

Prediction

A metal consists of ions (metal cations) surrounded by electrons. These electrons are free to move through the structure of the metal. When there is no applied external electric field, the electrons move randomly. When an electric field is applied, however, the electrons will be attracted towards the more positive potential and the cations towards the more negative potential. It is only the electrons which are free to move, these travel towards the positive potential. The electrons are accelerated towards the positive potential and their kinetic energy increases. But as they move through the metal they collide with the metal ions, this has the effect of slowing the electrons down and transferring some of the electron’s energy to the metal. In addition to slowing the electrons down, energy is transferred to the metal and this acts to heat up the metal. As the metal gets hotter and hotter, the metal ions vibrate more and more and so the number of collisions between ions and electrons increase, in effect the resistance to current flow increases.

Conclusion

My conclusion is a very limited one, it is only suitable a wire of length up to 90cm. This conclusion may not necessarily be the same for other lengths of wire. Also the results are only for one type of wire. The results and therefore the conclusion would be different for another type of wire as it may conduct better resulting in a larger current. The results are at a constant voltage of 1 volt. If the voltage was higher there would be a larger current as the electrons would be provided with more energy giving them more of a chance of passing through the wire. The cross sectional area of the wire was also the same in all the wires, this means that the conclusion that I have reached is only suitable for a nickel-chrome wire of cross sectional area 30 with a voltage supply of 1 volt.

To expand on my conclusion, I could expand on the experimental procedure. I could use the same experiment on different wire cross sectional areas and different voltages to see if they gave me a similar conclusion. I could also experiment with wires mad of different materials to see if my conclusion related to any other material of wire.

This student written piece of work is one of many that can be found in our GCSE Electricity and Magnetism section.

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