Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Static electricity wikipedia , lookup
Electrolysis of water wikipedia , lookup
Electrical injury wikipedia , lookup
Electric charge wikipedia , lookup
Chemical potential wikipedia , lookup
General Electric wikipedia , lookup
Electrochemistry wikipedia , lookup
Photoelectric effect wikipedia , lookup
Electric current wikipedia , lookup
Potential energy wikipedia , lookup
Electricity wikipedia , lookup
Examples • In a 9 volt battery, typically used in IC circuits, the positive terminal has a potential 9 v higher than the negative terminal. If one micro-Coulomb of positive charge flows through an external circuit from the positive to negative terminal, how much has its potential energy been changed? V q U Vb Va 0 9 q U 9q = -9V x 10-6 C U = -9V x 10-6 Joules U = -9 microJoules Potential energy is lower by 9 microJoules Examples A proton is placed in an electric field of E=105 V/m and released. After going 10 cm, what is its speed? Use conservation of energy. a E = 105 V/m d = 10 cm b v + V = Vb – Va = -Ed v U = q V U + K = 0 K = (1/2)mv2 K = -U (1/2)mv2 = -q V = +qEd 2qEd m 2(1.6 10 19 C)(10 5 Vm )(0.1m) 1.67 10 23 kg v 1.4 104 m s Electric potential due to a positive point charge Hydrogen atom. •What is the electric potential at a distance of 0.529 A from the proton? + r r = 0.529 A 1A =10-10 m • V = kq/r = 8.99*109 N m2//C2 *1.6*10-19 C/0.529*10-10m • V = 27. 2 J/C = 27. 2 Volts What is the electric potential energy of the electron at that point? U = qV= (-1.6 x 10-19 C) (27.2 V)= - 43.52 x 10-19 J or - 27.2 eV where eV stands for electron volts Total energy of the electron in the ground state of hydrogen is - 13.6 eV Also U= 2E = -27.2 eV. This agrees with above formula.