A refrigerator magnet holds a paper clip in midair. Acting the other way is the entire Earth. The magnet wins.
This lesson gives the second profile, the electromagnetic force: what it acts on, how far it reaches, and how strong it is.
You've already seen that any charge in an electric field experiences a force, and that the electric and magnetic forces are two aspects of this one electromagnetic force. That gives the first line of the profile: the electromagnetic force acts on everything with electric charge.
The second line gives the range: the electromagnetic force acts over unlimited range, growing weaker with distance but never reaching zero. That is the same shape as gravity's range line. Distance weakens the force, and no distance switches it off.
The third line gives the strength: the electromagnetic force is far stronger than gravity.
The paper clip shows the strength gap. A thumb-sized magnet lifts the clip against the pull of the entire Earth. One small magnet beats six septillion kilograms of planet.
Two charged balloons hang from threads on opposite sides of a room. Does an electric force act between them?
Both balloons carry electric charge, so the electromagnetic force acts between them.
The electromagnetic force acts over unlimited range, growing weaker with distance but never reaching zero.
The width of a room weakens the force; it does not end it.
Yes. The distance weakens the force, but the force is not zero.
In a hydrogen atom, an electron and a proton attract each other both electrically and gravitationally. Which attraction is larger?
Both particles have mass, so gravity attracts them to each other.
Both particles carry electric charge, so the electromagnetic force also attracts them to each other.
The electromagnetic force is far stronger than gravity.
The electromagnetic attraction is overwhelmingly larger.
The electromagnetic force acts on…
Two charged specks of dust drift far apart in space. Is there still an electric force between them?
Between two electrons, which force is stronger?
Fresh from a dryer, a sock clings to a shirt. The cling happens because the sock and the shirt…
A charged balloon is carried step by step away from a charged doorknob. What happens to the electric force between them?
A rubbed plastic comb lifts small paper scraps off a desk, against the pull of the entire Earth. What does this show?