Must a magnetic material touch the magnet to experience the force?
A magnet pulls a pin it never touches. A charged balloon pushes a second charged balloon aside across a gap. Earth pulls a falling apple through empty air. Three different forces share one trick.
In earlier grades you sorted forces into contact forces and non-contact forces. The three forces above all sit on the non-contact side. And physics gives their home regions one shared name.
Here are the three regions side by side.
Around the magnet, a magnetic material feels a force without touching anything. Around the charged balloon, a charged object feels a force without touching anything. Around Earth, any mass feels a force without touching anything.
Each region works on objects with one particular property: magnetic material, charge, or mass. That property is the region's right property.
The word is borrowed, not literal. A physics field is not grass, and not a glowing wall from a movie. It is a region of space where the right kind of object feels a force with nothing touching it.
A magnet turns a compass needle, a charged rod pushes a charged thread aside, and Earth pulls a skydiver. What do the three forces share?
A charged bead near a charged comb feels a push, with nothing touching it. Is the space around the comb a field?
Check the definition's three parts:
The space around the comb is a region.
The bead has the right property for that region: charge.
The bead feels a force there without contact.
Yes: the space around the comb is a field (an electric field).
Around a charged rod there is a region where a charged scrap of foil feels a force without touching. Is that region a field?
Wind pushes a kite across the sky. Is the moving air a field?
Check the definition's three parts:
The air touches the kite.
A push from touching is a contact force.
A field exerts its force without contact.
No: the moving air is not a field. The push is a contact force.
Type the name for a region in which an object with the right property feels a non-contact force.
So the magnet sits in the middle of a magnetic field. The balloon sits in the middle of an electric field. Earth sits in the middle of a gravitational field. And the apple falls because it has mass and sits inside that region.
Which of the following regions is a field?
A plastic bead with no charge sits near a charged sphere and feels no electric force. A charged bead in the same spot feels a push without touching. Which object shows that the region is an electric field?
Which statement is true of every point inside a field?