* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Magnetic fields
Introduction to gauge theory wikipedia , lookup
Condensed matter physics wikipedia , lookup
Anti-gravity wikipedia , lookup
Elementary particle wikipedia , lookup
Time in physics wikipedia , lookup
Fundamental interaction wikipedia , lookup
Speed of gravity wikipedia , lookup
Maxwell's equations wikipedia , lookup
Field (physics) wikipedia , lookup
Magnetic field wikipedia , lookup
Work (physics) wikipedia , lookup
Neutron magnetic moment wikipedia , lookup
Superconductivity wikipedia , lookup
Electric charge wikipedia , lookup
Aharonov–Bohm effect wikipedia , lookup
Electrostatics wikipedia , lookup
Magnetic monopole wikipedia , lookup
Electromagnetism wikipedia , lookup
Chapter 27 Magnetism 27-4 Force on an Electric Charge Moving in a Magnetic Field The force on a moving charge is related to the force on a current: Once again, the direction is given by a right-hand rule. Magnetic Force on a point charge Force on a moving charge ( F = q v´B ) Direction: Right hand rule F is Perpendicular to both v and Lay hand along v palm toward B +q Thumb points along F -q Thumb points opposite F = out of page Arrow coming at you B B = into page Arrow leaving you v F Magnetic Force on a point charge Direction: RIGHT Hand Rule Perpendicular to both v and B Here Into or Out of the page Run fingers along v, curl them towards B, •If q is positive, thumb points along F •If q is negative, thumb points opposite F Magnetic Force on a point charge • If q is + find the direction of F F v B F B F v B v Problem 17 • 17.(I) Determine the direction of for each case in Fig. 27–43, where represents the maximum magnetic force on a positively charged particle moving with velocity 27-4 Force on an Electric Charge Moving in a Magnetic Field Example 27-5: Magnetic force on a proton. A magnetic field exerts a force of 8.0 x 10-14 N toward the west on a proton moving vertically upward at a speed of 5.0 x 106 m/s . When the proton is moving horizontally in a northerly direction, the force on it is zero . Determine the magnitude and direction of the magnetic field in this region. (The charge on a proton is q = +e = 1.6 x 10-19 C.) 27-4 Force on an Electric Charge Moving in a Magnetic Field If a charged particle is moving (electron) perpendicular to a uniform magnetic field, its path will be a circle. What if you have a proton? 27-4 Force on an Electric Charge Moving in a Magnetic Field Example 27-7: Electron’s path in a uniform magnetic field. An electron travels at 2.0 x 107 m/s in a plane perpendicular to a uniform 0.010-T magnetic field. Describe its path quantitatively. 27-4 Force on an Electric Charge Moving in a Magnetic Field Problem solving: Magnetic fields – things to remember: 1.The magnetic force is perpendicular to the magnetic field direction. 2.The right-hand rule is useful for determining directions. The right-hand rule gives the direction. 3.Equations in this chapter give magnitudes only. 27-4 Force on an Electric Charge Moving in a Magnetic Field Charged particles in B-fields • • • Aurora Borealis: Northern Lights Aurora Australis: Southern Lights Due to ions (e- & p+) from the Sun – Travel from Sun to Earth in ~ 3 days • 93 million miles in 3 days ~ 30 million miles/day www.spaceweather.com Aurora on 11/20/03, Zagreb, Croatia. Photo by Hrvoje Horvat http://www.nasa.gov/mpg/143772main_SolarCycleCME_Reconnection.mpg Aurora Ions steered to poles by Earth’s mag. field – Collide with molecules in atmosphere • ionize particles, recombination produces light: Aurora – More energetic particles get closer to Earth http://www.swpc.noaa.gov/pmap/ Lorentz Equation Mass Spectrometer v = E1 B1 r= For selected speeds mv qB æ ö E m 1 r= ç ÷ qB çè B1 ÷ø Electromagnetic Flowmeter + v - - - - - - - B d E + + + + + + + B ∆V A flowmeter read the blood flow in organs, and determine the oxygen flow, nutrients, hormones and so on, and is connected to the body through a catheter and a voltage is applied. Charges build until forces balance! FE = FB qE = qvB v flow = E B = DV Bd We know B since we applied it. E is determined from V and the width of the artery d E=V/d 27-4 Force on an Electric Charge Moving in a Magnetic Field Conceptual Example 27-10: Velocity selector, or filter: crossed B E and E B fields. Some electronic devices and experiments need a beam of charged particles all moving at nearly the same velocity. This can be achieved using both a uniform electric field and a uniform magnetic field, arranged so they are at right angles to each other. Particles of charge q pass through slit S1 and enter the region where BB points into the page and E E points down from the positive plate toward the negative plate. If the particles enter with different velocities, show how this device “selects” a particular velocity, and determine what this velocity is. Problem 25