What causes the positive and negative forces on a magnet and the earth poles?
Same way you change it when it isn't raining, only a bit more wet.
We need the year make and model of your car. If you own an Audi or Volkswagen, forget it.
Magnetism I would imagine!
The core and mantel of the earth is primarily made of metal. The temperatures are so great that the metal is melted (except, supposedly, in the inner core, where the density of the metal makes it a solid). This melted metal flows around in the core, and through its movement creates the magnetic field. [A magnetic field is just an eletric field that is moving. In a melted metal, the electrons are able to move around more freely, causing the electric field. The motion of the liquid metal creates the magnetic field.]
A magnetic field is a field of force produced by a magnetic object or particle, or by a changing electrical field[1] and is detected by the force it exerts on other magnetic materials and moving electric charges. The magnetic field at any given point is specified by both a direction and a magnitude (or strength); as such it is a vector field.[nb 1 The complex mathematics underlying the magnetic field of an object is usually illustrated using magnetic field lines. These lines are strictly a mathematical concept and do not exist physically. Nonetheless, certain physical phenomena, such as the alignment of iron filings in a magnetic field, produces lines in a similar pattern to the imaginary magnetic field lines of the object. See the figure to the left. Magnets exert forces and torques on each other through the magnetic fields they create. Electrical currents and moving electrical charges produce magnetic fields. Even the magnetic field of a magnetic material can be modeled as being due to moving electrical charges.[nb 2] Magnetic fields also exert forces on moving electrical charges. The magnetic fields within and due to magnetic materials can be quite complicated and is described using two separate fields which can be both called a magnetic field: a magnetic B field and a magnetic H field. Energy is needed to create a magnetic field. This energy can be reclaimed when the field is destroyed and, therefore, can be considered as being stored in the magnetic field. The value of this energy depends on the values of both B and H.
