@YouKnowMe hi, I have finished lunch if you're still around.

@JohnRennie Draw the line of force(indicating field direction) of the magnetic field through and around (a) a single loop of wire carrying electric current, and (b) a solenoid carrying electric current.

What does "Lines of force" mean?

A line of force shows the direction of the force the field exerts on a charge.

(For a magnetic field this would have to be a hypothetical charge since there are no magnetic monopoles)

So suppose you are holding a charge in a field and you move the charge slowly so that you are always moving it in the direction of the force that the field exerts on it. The motion would trace out a line of force.

You may know them as field lines.

@JohnRennie Magnetic field lines?

Yes, or of course electric field lines if the field is electric.

Thanks :-)