To understand the fundamental building blocks of nature, scientists create large particle accelerators to accelerate and collide beams of particles. To understand the accelerators themselves, scientists create smaller machines to simulate the behavior of these beams of particles.
A small tabletop version was created using a ring stand from a chemistry laboratory, two metal spheres, and a power supply that creates an electrical potential of several thousand volts. When this voltage oscillates at 60 Hertz and drop small dust particles into the gap between the ring and the spheres, it is possible to clearly see that we are now trapping charged particles.
In our demonstration, the dust grains are charged and are alternately pushed and pulled by the oscillating voltage. Since they are heavy, and the voltage oscillates quickly, the particles never have time to get pushed or pulled all the way out of the system --- they stay trapped.