What affects the strength of an electromagnet?
The strength of an electromagnet depends on
-- the magnitude of the electric current in the wire coil,
-- the number of turns of wire in the coil,
-- the composition of the material in the core surrounded by the coil.
There are a couple of ways to increase the strength of a copper electromagnet. You could increase the current going through the wire or wrap more wire around it which increases the strength exponentially. You could also put in a soft iron core such as a nail which in essence becomes a magnet and increases the strength of the magnet.
The most basic experiment involves these materials: - several paper clips - your electromagnet If you want to test the strength of the electromagnet, put some paper clips at a nearby distance and see how many are attracted to the magnet. If you want to compare it with other electromagnets with different strengths, just record the numbers on a table.