You don't have a current meter in your underequipped lab.
So you make one out of a compass.
The wire you want to measure the current in is aligned with the North South line.
You place your compass directly under the wire at a distance of 10cm from the wire.
With no current flowing, the compass needle points due north.
When you turn on the current, the compass needle points 5 degrees west of north.
You now have enough information to find the current in the wire, and whether it's flowing north or south!
Hint: the strength of the horizontal component of Earths magnetic field in Orlando is 25 micro Teslas and points due North.
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