Investigation of the factors that affect the size of a current flowing in a wire.

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Investigation of the factors that affect the size of a current flowing in a wire

By Joseph Davies 11E

I will investigate the various factors, e.g. length of the wire, cross-sectional area of the wire. I will found out how they affect the size of the current flowing in a nichrome wire at a constant voltage.

The factors that affect the size of a current flowing in a wire are:

  1. Voltage.

   Voltage is proportional to the current, providing the temperature remains constant. I know this from Ohm’s Law. The formula for this is:

V   =   I   X   R

voltage          current        resistance

   If I rearrange this formula so that the current is the subject then     I=V/R, this shows that as the voltage increases so will the current. E.g. I=V(2) = 1amp, but if v=4 then I = V(4) = 2amps

           R(2)                                              R(2)

   Voltage is the kinetic energy of the electrons so the larger it is, the faster the electrons will flow.

  1. Cross-sectional area

   The resistance of a wire is inversely proportional to its cross-sectional area. The larger the cross-sectional area, the larger the current.

3. Temperature

   As the temperature lowers, the size of the current increases. Because:

                                                                     

Because electrons collide with the metal ions and these collisions oppose the flow of electrons. As the temperature increase, the atoms of metal vibrate more. So there is less space for electrons to flow. If the temperature is lower, then there will be less vibration from the metal ions so fewer electrons will pass through.

  1. Material of wire

   Different materials have different properties to conduct electricity. For example for a given voltage, a metal would have a larger current than wood. Depending upon their atomic structure, different materials will have different amounts if free electrons. Therefore, the various conductors used in wires, have different values of resistance. Good conductors will have lower resistance.

I am going to investigate how the length of a wire affects the size of a current at a constant voltage.

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  I predict that if the length is doubled then the current will halve, because the resistance of the wire is directly proportional to the length of the wire. As the length of the wire is increased, the amount of energy lost through heat increases. The additional energy loss subtracts from the energy being transferred through the conductor, which results in a decrease in current flow for a given constant voltage.

   Voltage across the wire accelerates the electrons; the electrons lose the kinetic energy in collision with metal ions. So they have to be accelerated again – and the process ...

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