Magnetic Field
Magnetic Field is the invisible force around a magnet that pulls on metals and makes compass needles move.
Set a fridge magnet on a table and push paper clips toward it one at a time. The clips close to the magnet snap to it fast, but the ones farther away just slide in slow. Past a certain point, the clips sit still — the pull can't reach them. That ring of reach around the magnet is its field.
Explaining magnetic field by grade level
A magnet has a force around it you cannot see. This force can push or pull on some metals. A compass has a tiny magnet inside it. That hidden force is what makes the compass needle spin and point a new way.
Projects that explore magnetic field
A magnetic field is invisible, but its effects are real and measurable. When solar storms disturb Earth's magnetic field, a hanging magnet swings several degrees within hours. A small mirror on the magnet reflects a light spot onto a wall, making those tiny field shifts visible.
A magnetic field grows stronger when more wire wraps around a metal core. A steel bar with 100 wraps picked up 18.15 grains of iron filings. A bar with only 50 wraps picked up 9.9 grains. The invisible force pulling on those filings got stronger with each added layer of wire.
A reed switch is a tiny glass tube with metal contacts inside. A nearby magnet pulls those metal contacts closed to complete a circuit. In this project, a nail wrapped in wire becomes an electromagnet. Each time a spinning magnet passes the reed switch, the magnetic field pulls the contacts together, closing the circuit.
When you touch a wire to a battery, the flowing electrons create a magnetic field around the wire. That invisible force pushes on the magnetized compass needle, swinging it away from north. Remove the wire and the needle returns to north, showing the field disappears when current stops.