Magnetic experiments are some of my boys’ favorite activities. This time, I decided to hide a bunch of items in some sand, make some magnetic wands, and let them try to fish out the magnetic objects. So they knew how many items to retrieve, I placed squares on a piece of paper (one paper was filled with enough squares for the magnetic items, and the other was filled with enough for the non-magnetic items). When they filled up all the squares, they knew they had retrieved all the items. 
The boys all enjoyed this activity so much! Oliver renamed his wand the “metal detector” and proceeded to walk around the house touching it to doorknobs, lamps, the radiators, and even tried to put away the silverware from the dishwasher with it! That was a bit painstakingly slow, but you know how that goes. 
Have fun exploring!
Seriously, the activities you do with your boys look so fun I want to do them for myself ;D