Presentation on theme: "OLIVER MANHEIM Drift Velocity!. What is drift velocity? The average velocity that a charged particle attains due to an electric field. In a metal wire,"— Presentation transcript:
What is drift velocity? The average velocity that a charged particle attains due to an electric field. In a metal wire, electrons move around rapidly and randomly. If there is an electric field through the wire, the vibrating electrons will drift in one direction—the speed at which they move is the “drift velocity.”
What does drift velocity depend on?! Charge (q) Current (I) Cross sectional area (A) Number of charged particles per unit volume (n)
How is drift velocity calculated?!? drift velocity current no. of particles per unit volume charge cross sectional area
Where did that come from?!?! Watch this informative video for an explanation of drift velocity, a basic derivation of the equation, and a sample problem.this informative video The drift velocity of charge in a conductor by fizzicsorg http://www.youtube.com/watch?v=KgbqPKZU5IA
One more example?!?!? Find the drift velocity of electrons in a copper wire with a diameter of 1 mm and a current of 3 A. The density of copper is 8.94 g/cm 3. The charge of an e - is 1.6×10 −19 C. 1. Find the number of electrons per unit volume. From the density of 8.94 g/cm 3, or 8.94x10 6 g/m 3, and the atomic number of copper, 63.546 g/mol, we calculate 140685.5 mol/m 3. Using Avogadro's number, we can find that the number of electrons is 8.5x10 28. Therefore n = 8.5x10 28 electrons per m 3. 2. Find the cross sectional area. I = 3 A n = 8.5x10 28 A = 8x10 -7 m 2 q = 1.6x10 -19 C A= πr 2 = π (½*0.001) 2 = π(0.0005) 2 = 8x10 -7 m 2 3. Plug values into drift velocity equation and solve. V d = 3 / (8.5x10 28 * 8x10 -7 * 1.6x10 -19 ) … V d = 0.00028 m / s
References! (Look at them if you need more help.) http://resources.schoolscience.co.uk/cda/16plus/copelech2pg3.html http://en.wikipedia.org/wiki/Drift_velocity http://physics.bu.edu/~duffy/semester2/c09_driftvelocity.html This site has an applet that might interest you!