Circuits and Electromagnets
Series circuits connect all components in one single loop - if one bulb breaks, everything stops working because there's only one path for electrons. Parallel circuits create multiple loops, so if one component fails, current can still flow through the other branches.
Here's where things get interesting: flowing electrons create magnetic effects. When you wrap current-carrying wire around an iron nail, you've built an electromagnet that can be switched on and off by controlling the current.
Bar magnets have permanent north and south poles that create constant magnetic force. Only iron, nickel, and cobalt are truly magnetic elements. Electromagnets give you control - turn the current on for magnetic force, turn it off to stop the magnetism.
Remember: Electromagnets are temporary and controllable, whilst bar magnets create permanent magnetic fields you can't switch off.