coulomb%27s%20law

# coulomb%27s%20law - 1 Electric Charge and Coulomb’s Law c...

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Unformatted text preview: 1 Electric Charge and Coulomb’s Law c Electric charge b The positive charge and negative charge: Matter is made of atoms. Inside an atom, there is the nucleus that is surrounded by electrons. Inside the nucleus, there are two particles called proton and neutron. The smallest nucleus contains only one proton. This is the nucleus inside a hydrogen atom. Proton and electron attract each other. Proton and proton, electron and electron repel each other. This is a property of these matters (proton and electron) and we call it charge . Electric charge is a property of matter that can cause attraction and repulsion. We call the charge carried by electrons “negative (- e) ” and the charge carried by protons “positive (+ e )”. Charge is a value, or a scalar, not a vector. It is fully described by a number. 2 Electric Charge and Coulomb’s Law c The unit of electric charge The SI 1 unit for charge is the coulomb. An electron or a proton has a charge of magnitude e = 1.602 18 × 10- 19 C (coulombs). Some scientists, chemists in particular, use another unit, the esu or electrostatic unit . One esu equals 3.335 64 × 10- 10 C. To provide you with an idea of the magnitude of a coulomb, approximately 0.8 C of charge flows through a 100 watt light bulb every second. Or about 5 million trillion electrons every second. The rate of charges flowing through a conductor is called a current. We will get to this a few chapters later. No one has ever seen the charge, but we sure all see its effect in everyday life: electrostatic discharge in dry winter days to all the appliances (lights to motors to cell phones) that are powered by electricity. How much more do we know about the charge? 1. The International system of Units, more reading: http://physics.nist.gov/cuu/Units/index.html . 3 Electric Charge and Coulomb’s Law c Charge and charge up b When the numbers of electrons and protons in an object are the same, we say that this object is (electrically) neutral. When they are not, we call it charged....
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coulomb%27s%20law - 1 Electric Charge and Coulomb’s Law c...

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