An electromagnet is made by winding plastic-coated copper wire around an iron nail and joining the wire ends to a battery. What does the plastic coating on the wire do?

In a working electromagnet the wire is wound on an iron core and its ends are connected to a battery. What is the battery's job in this build?

A student unhooks both wires of a working electromagnet from the battery and connects each one to the opposite terminal. What changes?

A coil of wire connected to a battery lifts only one paper clip when it is empty inside, but lifts many when an iron rod is slid into the middle. What does the rod do?

In an electromagnet the wire is not left straight; it is wound into many turns around the core. What do those turns of wire do?

An electromagnet with 20 turns of wire lifts 6 paper clips. The student rewinds the same wire as 60 turns on the same nail, using the same battery. What is the likely result?

Keeping the same coil and the same nail, a student connects a second identical battery into the circuit so a larger current flows. How does the electromagnet's strength change?

A student takes the iron nail out of an electromagnet's coil and slides a wooden pencil of the same size into its place, changing nothing else. What happens to the clips it lifts?

A class electromagnet that lifted a pile of clips last month now lifts only one or two. Nobody has rewound or rebuilt it. What is the most likely cause?

Two students use identical wire, nails and batteries. One packs the turns tightly side by side; the other spreads the same number of turns far apart along the nail. Whose magnet is stronger, and why?

A student adds a long extra length of wire between the coil and the battery, without adding any turns. The magnet now lifts fewer clips. What best explains the drop?

Keeping the turns and the battery the same, a student swaps a thin iron nail for a thicker iron bolt of the same length. The magnet lifts more clips. What does this show?

A recycling plant must pull steel cans off a moving belt, carry them sideways and drop them into a bin. Which magnet suits the job better, and why?

A teacher wants to hold a paper chart against a steel classroom board all week, with no wires and nothing plugged in. Which magnet suits this job, and why?

A door lock must stay shut while current flows and spring open by itself the moment the building loses power in a fire. Which magnet does the lock need, and why?

The north-seeking end of a hiker's compass needle points toward the Arctic. Opposite magnetic poles attract. What kind of magnetic pole lies near Earth's geographic North Pole?

A bar magnet is cut cleanly in half across its middle with a hacksaw. What is true of the two pieces afterward?

Two bar magnets rest on a smooth table. A student slowly slides the north end of one toward the north end of the other. What happens as the ends come close?

A bar magnet is hung level from a thread tied around its middle and left to settle in a still room, away from other magnets. What does it do?

A bar magnet is rolled through a tray of loose iron filings and then lifted out. Where do most of the filings cling to it?