Electromagnets have long since been a science fair staple because of their impressive functionality despite the relative ease of construction. With some inexpensive purchases from your local hardware store, such as a lantern battery and some magnet wire, you can test a variety of hypothesis related to magnetism. For example, you can test demonstrate the strength and weaknesses of an electromagnet as it relates to the type and size of wire used, as well as the number of times the wire is coiled.
Use the simple concept of opposing magnetic fields to create a basic motor. Create a simple electromagnet on a basic axle, so that it can revolve. When you place a magnet with fixed north and south poles, known as a permanent magnet, near your free-spinning electromagnet, the opposing fields will cause the electromagnet to revolve on the axle at varying speeds, creating a basic motor. This simple concept can be the foundation for a variety of electrical and engineering experiments, such as the direct relationship between revolutions per minute (RPM) and the strength of either magnet.
Budding engineers can test the load-bearing capacity of different types of bridges by constructing inexpensive and reduced-scale models using balsa wood. Competitions exist that require students to build bridges weighing no more than 100 gm, but that can support more than 200 kg of weight. Due to the research and engineering knowledge required, such a project would be ideal for a group of several advanced 7th graders.
Demonstrate some fundamental engineering concepts through the classic drop test. By packing a variety of objects, from a vulnerable egg or piece of glass to sturdier wooden or metal objects, inside a box of differing packaging materials, such as packing peanuts or newspaper, students can conduct many different of experiments related to gravity and shock absorption. This type of experiment is ideal for students new to science projects who wish to exhibit a thorough testing process with an experiment that's relatively easy to setup, as it requires numerous iterations in a variety of scenarios without the need to construct working models or prototypes.