Household Magnets - How Things Work - Slides | PHYS 140, Exams of Classical Physics

Download Household Magnets - How Things Work - Slides | PHYS 140 and more Exams Classical Physics in PDF only on Docsity! 11.1 Household Magnets First, some fun finds from students… A vehicle with static and dynamic stability! (Madelin Woods) The anti-TASER jacket (Steven Buran) New ideas for today: • Magnetism • Refrigerator magnets • Electromagnets Observations about Household Magnets  Two magnets can attract or repel  Magnets can stick to certain metals  Magnets affect compasses  The earth seems to be magnetic  Some magnets use electricity to operate Magnetic Poles  Two types: north & south  Like poles repel, opposites attract  Forces increase with decreasing separation  Analogous to electric charges EXCEPT:  No isolated magnetic poles ever found!  Net pole on an object is always zero! Clicker Question: Suppose you have a long bar magnet with a north pole at one end and a south pole at the other. If you break it in half, will the two new ends: A. Attract B. Repel C. Neither Click me Magnetic Fields  A magnetic field pushes on magnetic pole  The magnitude of the field is proportional to the magnitude of the force on a test pole  The direction of the field is the direction of the force on a north test pole But isolated magnetic poles don’t seem to exist! Torque on a dipole N S • Magnitude of torque proportional to magnetic field • Torque always acts on dipole to line it up with field I prefer to talk about the torque from a magnetic field on a dipole Torque on a dipole N S • Magnitude of torque proportional to magnetic field • Torque always acts on dipole to line it up with field I prefer to talk about the torque from a magnetic field on a dipole Electromagnetism I  Magnetic fields  Push on magnetic poles (or torque magnetic dipoles)  Bend moving electric charges  Electric fields  Push only on electric charges