1. Observations of Electrical Phenomena ENGR 101 Lecture

2. Plato’s allegory of the cave … A gathering of people who have lived chained to the wall all their lives Fire is lit behind the prisoners Puppets perform in front of fire Shadows are cast on the wall The prisoners give names to the shadows.

3. Electric Current Flow of electric charge - - - - - - - - - - - - - - - - - - - - - - - - Not flow!

4. Electric Current Flow of electric charge - - - - - - - - - - - - - - - - - - - - - - - - Flow!

5. Electric Forces Electric field at point P due to single charge Electric force on a test charge placed at P F

6. -------------------------- Voltage=> Electric Field +++++++++++++++ ++ V Distribution of charge +V- +++

7. Measuring voltage … Voltage is measured across the terminals of the resistor, and conveys a global picture of cause and effect, but does not convey the information at the micro level.

8. Measuring current … The conductivity of a material is a measure of how easily electrons can travel through the material under the influence of an externally applied electric field.

9. Capacitance (Depends on geometry)

10. Magnetic Forces Electromagnetic (Lorentz) force Magnetic force

11. Magnetic Force on a Current Element Left-Hand Rule for force on a wire of current due to magnetic field F (B going in to sheet of paper) F

12. Applications Motor Railgun