A student sets up an experiment to investigate the magnetic field surrounding two identical permanent bar magnets. The magnets are aligned coaxially on a flat sheet of paper with their North poles facing each other, as shown in the diagram below.
a.[3]
Describe how the student could use iron filings and a small plotting compass to find both the pattern (shape) and the direction of the magnetic field lines on the sheet of paper.
b.[2]
Describe the shape and direction of the magnetic field lines in the region between the two facing North poles.
c.[2]
If a magnetic compass is kept away from any local magnets or current-carrying wires, it always points in a North-South direction. Explain how this observation provides evidence about the Earth's core.