Lecture II. Electricity


Types of energy

But: easily-stored not transportable/usable; end-use not storable.
Energy "Form"Examples
Easily-stored Chemical: coal, oil, nat. gas, food
Gravitational: water behind a dam
Nuclear: uranium, plutonium, hydrogen isotopes
Easily-transported Electrical, chemical, solar (how?)
End-use Kinetic: transportation, industrial
Thermal: residential, industrial, commercial
Radiant: residential, commercial

Energy: Stored to End-Use

Total resources: 99.2 Quads Energy: Stored to End-Use

Total US usage: 97.2 Quads (incl nonfuel but not exports)

Previous version

Electricity Fundamentals.

Assume "charges" can be moved.

  1. Charge unit: Coulomb (C) (~1019 electrons)
  2. Voltage unit: Volt (V), esp., voltage difference.
  3. Energy . 1 C in 1 V difference has 1 J energy; voltage difference cause charge flow: current.
  4. Current (I) unit: ampere or amp (A) = C/s.
  5. Resistor allows current flow under voltage diff.
  6. Ohm found relation: V = R I.
    R unit: Ohm (Ω) = V/A.
  7. Power dissipated in a resistor is work done in moving charge thru voltage difference;
        if C V is energy, then
        then (C/s) V = I V is rate of doing work.
        By Ohm, power dissipated is I V = I2 R.
    This dissipation heats the current-carrying wire.
  8. Bad news. Transporting electric power involves the dissipation of energy. Transmission losses lower efficiency.

How to create voltage difference

  1. Magnets exist (don't ask how).
  2. Faraday discovered current-carrying wire moving in a magnetic field produces voltage.
  3. Motors reverse process. Wire in magnetic field with applied voltage difference is moved.
  4. Engineers have found efficient ways to


To cite this page:
Electricity: Chapter 4
[Saturday, 20-Oct-2018 21:56:26 EDT]
Edited by: wilkins@mps.ohio-state.edu on Wednesday, 24-Sep-2008 17:51:41 EDT