A Jacob's Ladder passes a high voltage electrical current into two metal rods. To complete the electrical circuit, the current must jump from one rod to the other. When the current arcs between the rods, it heats the air around it. The hot air rises, carrying the current up the rod with it. When the arc reaches the top of the rod, it dissipates and a new arc forms at the bottom of the rod. The entire project is an excellent experiment in how electricity works.
Use a neon sign power inverter or an oil burner's ignition transformer for the power source.
Jacob's Ladder's use extremely high voltage levels, which are inherently dangerous. Electrical currents can jump several inches from the air, delivering a dangerous shock. Keep your Jacob's ladder several feet away from all objects, people or animals whenever it is plugged in.
Cut the No. 4 American wire gauge (AWG) wire into two even 3-foot long lengths.
Drill two holes in the center of the wood block about 1/2-inch apart and 1/2-inch deep.
Insert one end of one of the lengths of No. 4 AWG wire into one hole. Insert the other end of the other length into the other hole.
Pull the tops of the two wires away from each other so that they are at least 1-inch apart at the top.
Wrap one of the high-voltage output wires from the power inverter around the base of each of the No. 4 AWG wires. Keep the two high-voltage wires as far from each other as possible when you run them to the No. 4 AWG wires to prevent premature arcing.
Position the entire assembly in the middle of a room with hard floors and no nearby objects. Plug the power inverter into a switched electrical outlet currently switched off.
Switch the electrical outlet on and watch the electrical arc climb Jacob's Ladder.