Lec18 - 18-1Physics IClass 18Coulomb’s LawRev 08-Mar-07 GB18-2Forces Known to Physics(Review)There are four fundamental forces known to

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Unformatted text preview: 18-1Physics IClass 18Coulomb’s LawRev. 08-Mar-07 GB18-2Forces Known to Physics(Review)There are four fundamental forces known to physics:•Gravitational Force (“yesterday’s news”)•Electromagnetic Force (start today)•Weak Nuclear Force•Strong Nuclear Force(All forces we observe are comprised of these fundamentalforces. Most forces observable in everyday experience areelectromagnetic on a microscopic level.)18-3A New Property of Matter -Charge•Charge comes in two types: positive and negative.•NETcharge can neither be created nor destroyed.(Principle of Conservation of Charge)•However, positive and negative charges can be separated or combined.•Charge is quantized – the smallest unit of charge (magnitude) innormal experience is the charge of the electron or proton, “e”.(All charges are integer multiples of this unit.)•By arbitrary historical convention, the charge of an electron is negativeand the charge of a proton is positive.Neutral H+e chargeelectron-e charge0 chargeproton18-4Conservation of Chargeneutronanti-neutrino0 chargeproton+e charge0 chargeelectron-e chargeCharge is even conserved in nuclear reactions.Here is what happens to a free neutron (outside anucleus) in about 12 minutes:This is an example of the weak nuclear force (beta decay).18-5Coulomb - A Man, A Unit, A LawCharles Coulomb, 1736-1806Coulomb invented a delicate torsion balance withwhich he was able to measure the forces betweencharged and magnetic objects with sufficientaccuracy to verify a previous conjecture that themathematical formula for electromagnetic forceshould resemble the formula for gravity.The unit of charge is named after Coulomb, abbreviated C.1.0 C = 6.24150975 × 10+18e1.0 e = 1.60217646 × 10–19COne Coulomb is a lot of protons!18-6Coulomb’s Law ofElectrostatic Force)rˆ(rqq41F221-επ=The meaning of each term: F: Electrostatic force on charge 1 from charge 2. 41επ: Electrostatic force constant = 8.98755 × 10+9N m2/C21q: Value of charge 1, positive or negative....
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This note was uploaded on 12/15/2010 for the course PHYS 0001 taught by Professor Nayak during the Spring '10 term at Rensselaer Polytechnic Institute.

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Lec18 - 18-1Physics IClass 18Coulomb’s LawRev 08-Mar-07 GB18-2Forces Known to Physics(Review)There are four fundamental forces known to

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