Exam 2 Resistivity conductivity Transfers electricity well resistivity R resistance Voltage V IR Power P IV I R V R Prevents the transfer of electricity Biot Savart point source Magnetic Fields Magnetic Force F q E v x B Thumb is in the direction of the force Fingers are in the direction of the velocity Curl your ngers to get the magnetic eld Remember to use RHR if the particle is positive and LHR if the particle is negative Dipole Moment Vector Dipoles always align with the B eld If the dipole is not aligned with the B eld the dipole feels a torque IA and x B where is the magnetic dipole moment If the B eld is non uniform the dipole feels a force F I L x B for a straight wire F I s x B otherwise Ampere s Law B s I J n a where J I A Pay attention to symmetry Cylinder envision as a circle Slab of charge with an Amperian loop Use RHR to determine the direction of the B eld Solenoid envision it cut in half On one side the current is going into the page and on the other Magnetic eld on the outside of the solenoid is zero B In h Toroid a solenoid wrapped in a circle The current on the inside is going one direction and is going the opposite direction on the outside Wrap your ngers around to get the current Your thumb will be in the tangential direction of B Practice Problems 2014 Exam 2 Spring 1 2014 Exam 3 Spring 1
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