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## Physics library

### Course: Physics library>Unit 11

Lesson 1: Charge and electric force (Coulomb's law)

# Triboelectric effect and charge

Learn the physics behind why a balloon clings to things after you rub it on a sweater.

## Want to join the conversation?

• Why was it decided that 1 C would equal 6.24 x 10^18 electrons? I realize that assigning the charge of 1 C to 1 electron would be impractical in daily life because we use such large currents, but who came up with that number and how?
• The Coulomb was initially defined based on the Ampere, which was then later determined to be approximately equal to that many electrons/protons. However, in the interest of making more accurate definitions, scientists are proposing to set the definition of the Coulomb, and thereby the Ampere, based on the fundamental charge.
• What "material(s)" are protons, or neutrons, or electrons made of?
• Protons and neutrons are composed of quarks. Quarks and electrons are fundamental particles and therefore not made of anything smaller as far as we currently know.
• I don't understand what charge is. An atom can have a charge because its electrons and protons have a charge. But what do we mean when we say that an electron has a charge? Why do they have a charge?
• Nithish,

A charge is a property of that particle, in the same way that the mass, and spin of a particle is also an inert property. As to why they have these properties, that's the real question.
• At 10.30. How is the reciprocal of the equation derived?
• You simply make a reverse of it. `1 / (6.24 * 10^18) = 1.6 * 10^-19`
• Why doesn't the hair tip attract with the bottom of the hair as both are oppositely charged?
• The hair is rooted to your skin, thus being grounded
• At when Sal said that 1C=6.24 * 10^18 why this value only? Any specific reason or formula?
• The formula is
Q= n.e or charge is equal to the number of electrons times the charge if 1 electron . To find the number of electrons in 1 C of charge we divide 1 from the charge of 1 electron , i.e, 1.6 *10^-19 . After solving it comes out to be 6.25*10^18 electrons
• At , in the atom model, wouldn't the electrons stick to the nuclei since Sal said different charges attract each other?
• That's because the electrons are orbiting. Means they're having enough speed to overcome electromagnetic forces but not enough speed to escape the atom.
• Have any idea of what force sticks together the protons inside a nuclear?