What it does
Everything is made of atoms with positive protons and negative electrons, and a thing with equal amounts of both is neutral. When two different materials are rubbed, a few electrons move from one to the other. The one that gains electrons becomes negative, and the one that loses them becomes positive. Here a balloon rubbed on wool gains electrons, so the balloon shows minus signs and the wool shows the same number of plus signs. Rubbing never makes charge, it only moves it, so the total stays zero.
A second picture hangs two balloons side by side. Like charges repel and unlike charges attract, so they swing apart or together. It follows the Class 8 Science topic on forces, where friction and electrostatic force are called contact and non-contact forces. For another push-and-pull picture try balanced forces, and for the maths of the force use coulomb forces.
How to use it
- Slide Rubs of balloon A and watch charges collect on the balloon and the wool.
- Tick Scatter small bits of paper to see them jump to a charged balloon.
- Choose what happens to Balloon B and watch the two balloons swing.
What each setting does
- Rubs of balloon A: each rub moves one more unit of charge from wool to balloon.
- Balloon B: negative (rubbed on wool), positive (electrons rubbed off) or not rubbed at all.
- Rubs of balloon B: how much charge B has.
Worked example
Rub balloon A five times: A has −5 and the wool has +5, and −5 + 5 = 0. If B is also rubbed on wool 5 times, both balloons are −5, the product (−5) × (−5) = +25 is positive, so they repel.
FAQs
Why do the paper bits jump? The charged balloon pulls the nearby side of each bit, so it moves up. Real paper is neutral overall, which this model only hints at.
Why does it work best on dry days? Moist air lets charge leak away; this model ignores that.
Are the numbers real? No. Real balloons hold billions of electrons, and the picture is exaggerated.
Where the numbers come from
- Charging by friction, conservation of charge, attraction and repulsion of charges, force proportional to q₁q₂ ÷ d² (Coulomb's law): standard school physics. Charge is counted in whole made-up units and the swing of the balloons is exaggerated. Drawings are fibub's own.
Standard scientific values, such as constants, atomic weights and melting points, are facts found in every textbook; we name where ours were checked. If you are an author or publisher and want a value, a credit or a table changed or removed, tell us and we will act quickly.
Last updated 2026-11-10.