# Magnetism (sec. 27.1) Magnetic field (sec. 27.2) Magnetic field lines and magnetic flux (sec. 27.3) Motion of charges in a B field (sec. 27.4) Applications

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• Slide 1
• Magnetism (sec. 27.1) Magnetic field (sec. 27.2) Magnetic field lines and magnetic flux (sec. 27.3) Motion of charges in a B field (sec. 27.4) Applications - moving charged particles (sec. 27.5) Magnetic force on conductor with current (sec. 27.6) Force and torque on a current loop (sec. 27.7) Direct current motor(sec. 27.8) The Hall effect(sec. 27.9) Magnetic Field & Forces Ch. 27 C 2009 J. Becker
• Slide 2
• Forces between bar magnets (or permanent magnets )
• Slide 3
• Earths magnetic field (Note the N-S polls of magnet!)
• Slide 4
• Compass over a horizontal current-carrying wire
• Slide 5
• Magnetic force acting on a moving (+) charge
• Slide 6
• Magnetic field lines associated with a permanent magnet, coil, iron-core electromagnet, current in wire, current loop
• Slide 7
• MAGNETIC FLUX through an area element dA
• Slide 8
• Orbit of a charged particle in a uniform magnetic field is a circle R = m v / q B
• Slide 9
• The Van Allen radiation belts around the Earth
• Slide 10
• Velocity selector for charged particles uses perpendicular E and B fields q v B = q E v = E / B
• Slide 11
• Mass spectrometer uses a velocity selector to produce particles with uniform speed. And from R = m v / q B we get q / m = v / B R
• Slide 12
• Force on a moving positive charge in a current-carrying conductor: F = I L x B L I I For vector direction use RIGHT HAND RULE
• Slide 13
• Magnetic force on a straight wire carrying current I in a magnetic field B Right hand rule F = I L x B
• Slide 14
• Magnetic field B, length L, and force F vectors for a straight wire carrying a current I
• Slide 15
• Components of a loudspeaker F = I l x B
• Slide 16
• Forces on the sides of a current-carrying loop in a uniform magnetic field. This is how a motor works!
• Slide 17
• Right hand rule determines the direction of the magnetic moment ( ) of a current-carrying loop
• Slide 18
• Torque ( x B) on this solenoid in a uniform magnetic field is into the screen thus rotating the solenoid clockwise
• Slide 19
• Current loops in a non-uniform B field
• Slide 20
• Atomic magnetic moments in an iron bar (a) unmagnetized (b) magnetized (c)Torgue on a bar magnet in a B field
• Slide 21
• Bar magnet attracts an unmagnetized piece of iron; the B field gives rise to a net magnetic moment in the object
• Slide 22
• A simple DC motor
• Slide 23
• The Hall effect forces on charge carriers in a conductor in a B field. With a simple voltage measurement we can determine whether the charge carriers are positive or negative.
• Slide 24
• A linear motor
• Slide 25
• Electromagnetic pump
• Slide 26
• See www.physics.edu/becker/physics51 Review C 2009 J. F. Becker