Homemade compass

We decided to build our own compass to help orient us for our stargazing. We magnetized a paperclip using our dangerously powerful- magnet (rubbing the paperclip across the magnet many times). We filled a container with water and put our now magnetized paperclip on a piece of cork in the water. The paperclip and cork slowly rotated until it was oriented north-south. We spun the cork around multiple times and it kept re-orienting itself. Pretty cool to see this invisible force at work (although next time I'll use a round piece of cork so it doesn't get stuck on the edge of the container without being able to turn). Jr. Scientist A liked the experiment, but I have a sense that the underlying concept of the earth having a magnetic field was a little too advanced.

Electromagnets

After previous unsuccessful attempts to make an electromagnet (and my clear deficiency in electrical experiments), we turned to my first science teacher, Dr. A, for a little help. After finding the right type of wire (who knew there's a lightly insulated wire labeled specifically for making electromagnets - well I didn't, but thankfully Dr. A did!), we quickly had our electromagnet up and running, complete with a light switch that turned the magnet on and off. Jr. Scientist A had fun flipping the switch on, picking up metal objects like paperclips and silverware, and then flipping the switch off and watching them drop. Some paperclips did get temporarily magnetized, making the dropping effect a little less dramatic and the concept a little less clear, but it was still quite a success.

Diving pen cap

We made a pen cap that dives on command. We took a pen cap, attached a string loop around it and added four paper clips to the loop as weights. We then filled a big soda bottle with water until it was almost completely full. We dropped the pen cap into the bottle and screwed the top on tight. When we squeezed the middle of the bottle, the pen cap sank because the air bubble inside it was compressed. When we let go, the air bubble expanded again and the cap floated back to the top. It took a little practice to get the weighting and water level right. When the cap capsized, causing the air bubble to escape and the cap to sink to the bottom, we used a magnet to drag the paper clips and cap to the top so we could reach in and pull it out without emptying the bottle.

Invisible forces

Materials
clear tupperware
pen
string
paper clip
magnet

Results
Success

Working theory
Since magnetic fields can't be seen, if we tether a paper clip and put something between the paper clip and the magnet, the magnetic field should be more apparent.

Experiment
We tied a paper clip on a string and tied the other end to the middle of a pen. We put the pen across the top of a clear tupperware with the paper clip just touching the bottom of the tupperware. We moved a magnet around under the tupperware, dragging the paper clip around through the tupperware without it getting "stuck" to the magnet.

Paper clip trains

Materials
paper clips
refrigerator magnet

Results
Success

Working theory
Ferromagnetic items (generally those with iron) can be magnetized. By rubbing a magnet across a ferromagnetic item like a paper clip, you can temporarily magnetize the item.

Experiment
We repeatedly rubbed a refrigerator magnet along a paper clip (always in the same direction - not sure if that matters). We were then able to use the magnetized paper clip to pick up another paper clip. By rubbing the magnet along multiple paper clips, we were able to make a series of magnetized paper clips. Placing them head to tail in a line we were then able to pull the whole train of paper clips by pulling the first one. We also magnetized other objects like certain keys, finding out that we could only magnetize objects that the refrigerator magnet would stick to (i.e. those that are ferromagnetic).