You can think of it as a bar magnet inside the sphere.

It turns out that you can think of the Earth as having a gigantic bar magnet buried inside.

The good old bar magnet under a piece of paper with iron filings on top.

Does the third side show a flux pattern like a long, very thin bar magnet?

Same with a bar magnet, except then there is some iron blocking its motion.

Now, take the bar magnet away and watch it point north again.

Put the compass aside and play with the two bar magnets.

The solenoid works just like a bar magnet, and therefore has many uses.

A bar magnet will require four lines, two at each end.

If we look at a standard bar magnet, there are two magnetic poles: north and south.