Magnetic field in a solenoid

I set up this circuit to investigate the magnetic field around and through a coil of wire. Such a coil of wire is called a solenoid. I used plotting compasses to show the direction of the field. First it is important to show that the compasses all point north when the current is turned off. To emphasise this I set up the solenoid along an east-west axis so all the compasses shown point across the axis.

Then I turned on the current. The compasses inside the solenoid point right, along the axis of the solenoid. Those above and below point left. the conclusion is that magnetic flux goes one way through the centre of the coil and then loops back round the outside of the coil. Thus there are said to be circuits of flux flowing through.

 Then I reversed the current and the magnets all dutifully pointed in the opposite direction.