1. Electrical Engineering Topic 1: Energy, Power, Information, Current, Voltage ENGR 1310

2. Electricity Basics Charge –The smallest unit of charge is that of an electron –Flowing charge is “Current” –Accumulated charge produces “Voltage”

3. Electrical Conductors Metallic bond –Electrons are shared –Valence electrons form “cloud” or “sea” of electrons –Electrons are free to flow –Causes metals to be good conductors

4. Electric Current Current  flow of positive charge “Free” electron Atom Electron Flow Current

5. A B C D E Electric Current Hole  concept used to explain current flow –Hole = absence of an electron –An electron (-) removed from a neutral atom leaves behind a “hole” (+)

6. Electric Current 1 “Coulomb” of charge is 6,241,506,360,000,000,000 electrons If 1 Coulomb flows through a wire in 1 second, we say the current is 1 ampere or 1 “amp” Current always “flows through”

7. Current Magnitudes Brain cell synaptic currents 10 -13 A Integrated circuits currents 10 -4 A Threshold of human sensation 10 -3 A Causes ventricular fibrillation 10 -1 A Household appliances 10 A Large industrial equipment 100 A Lightning bolt 1000 A

8. Power Power: the rate at which energy flows from one place to another –Units: Joules/second (also called a Watt) –Helpful to think of a Watt as an energy unit per time unit –Like “mach one” is a certain number of miles per hour Kilowatt = 1000 watts 1 horsepower = 745.7 watts

9. Voltage Voltage arises from accumulated charge being separated Opposite charges attract –Positive likes negative –Energy is required to separate them Like the ends of a stretched rubber band Rubber bands can be stretched to different lengths “Voltage” is a measure of how much energy each coulomb of charge contains

10. Voltage 1 “volt” means each Coulomb of charge can release 1 Joule of energy –A 12 Volt battery will produce 12 Joules of energy for every coulomb of electrons delivered 120 VAC

11. Voltage Voltage exists between two points, –NOT at an individual point The earth is a common reference point –“Ground” –Voltages with respect ground are like rubber bands with one end on the ground

12. Power Remember, power is the rate at which energy is transferred Electric Power is found by multiplying voltage and current

13. Power Question: How much power is supplied to a belt sander that draws 15 amps using “wall” voltage? Answer: 120 Volts x 15 Amps = 1800 Watts 1800 W = 1.8 kW

14. AC, DC, and all that DC stands for “direct current” and means the voltage and current are constant –All batteries supply DC power –“Cigarette Lighter Power” is DC AC stands for “alternating current” and means that the voltage and current “alternate” back and forth Grid-supplied electric power is AC, cycling 60 times every second, or at 60 Hz.