Mass Spectrometer Used to identify atoms and their

Mass Spectrometer • • Used to identify atoms and their concentrations in a sample of material. Between S 1 and S 2, molecules go straight if • • • After S 2, B produces circular motion • • • q. E=qv. B or v = E/B q v B’ = m v 2/r m = q B’ r/v = q B B’ r/E Found isotopes General Physics 2 Magnetism 1

E 8 – Topics to cover • • • Magnetic Force on a wire Torque on a wire Electric Motors - lab Creating currents in moving loops Eddy currents in moving conductors General Physics 2 Magnetism 2

Force on a wire • Magnetic force of a straight wire segment General Physics 2 Magnetism 3

Demo: Magnetic Force • Interaction between B field and current Moving charges are affected by B fields General Physics 2 Magnetism 4

Force on Current in B Field (for uniform field) General Physics 2 Direction of F • given by Right Hand Rule • fingers = I • bend fingers = B • thumb = F Magnetism 5

Think-Pair-Share • • (a) What is the magnitude of the force per meter of length on a straight wire carrying an 8. 40 -A current when perpendicular to a 0. 90 T uniform magnetic field? (b) What if the angle between the wire and field is 45. 00? General Physics 2 Magnetism 6

Torque on a wire • • A loop carrying a current will experience a torque which causes the loop to ROTATE! μ is the loop’s magnetic moment • Expresses the strength and south-to-north orientation of the loop’s equivalent bar magnet General Physics 2 Magnetism 7

Torque on a Loop • • • Forces on segments of a loop cause the loop to rotate Simplify by replacing loop with magnet • Fingers in direction of current, thumb represents NORTH pole of magnet Think about the loop as a magnet will rotate so that the north face of the magnet points in the direction of the magnetic field General Physics 2 Magnetism 8

Electric Motors - Torque • • In each orientation, which way will the loop rotate? Changing the direction of the current will keep the loop spinning General Physics 2 Magnetism 9

Commutator • • To change the direction of the current and keep the loop spinning, a commutator is used http: //www. walter-fendt. de/ph 14 e/electricmotor. htm General Physics 2 Magnetism 10

Eddy currents in moving conductors • • You can create a current in a metal plate by moving the plate through a magnetic field. Current density will be constant in the region of the magnetic field General Physics 2 Magnetism 11

Practice Problems • Magnetism: Worksheets 3 and 5 • Finish before next class General Physics 2 Magnetism 12

Group Problems • • • E 8 B. 1 E 8 B. 4 E 8 S. 5 General Physics 2 Magnetism 13