Theory: Charge • A property of particles that experience electromagnetic force • Two kinds of charge: positive and negative • Force due to charge obeys an inverse square law • Charge is measured in coulombs • • Electrons and protons each have the same size charge (but of opposite polarity) Charge magnitude = 1.6 * 10-19 coulombs

Theory: Current Current is charge in motion Most of the time we think about electrons moving through metallic wires The flow rate of charge is measured in couloumbs/second or Amperes (Amps) • charge/time = couloumbs/sec = Amperes 1 Amp = 1.6 * 1019 electrons / sec

Theory: Voltage • • • • • • • Voltage is the driving force behind current Voltage is the electrical potential energy a charge has due to its position in space • potential energy per unit of charge • "path independent“ Voltage is measured in Joules/Coulomb or Volts (V) Voltage is defined such that negatively charged particles are pulled towards higher voltages Potential energy can be converted into other forms of energy

Theory: Resistance Resistance is a property of materials Resistors are electrical components with known resistance • Resistor code Resistors convert voltage to heat Ohm's law describes the relationship between voltage and current flow through a resistor • V=IR • V is the voltage across the resistor • I is the current flowing through the resistor • R is the resistance (depends upon the material) Resistance is measured in Ohms, Ω

Assignment due by the start of class on 9/27 Work the following two lab exercises in the embedded systems lab across from the copier on the second floor of Rhodes Robinson. Please make and appointment to have the room opened. Submit the completed exercises electronically in Moodle or in hardcopy at the start of class on 9/27 Exercise 1 Exercise 2