Electricity Theory VIR PIV and Capacitors!!!

Energy PEg When an object is at some height in a gravitational field it is said to have gravitational potential energy, PEg

Energy Like gravitational fields causing masses to have potential energy, Electric Fields cause charges to have electric potential energy, PEE PEE is a type of mechanical energy MEtotal = KE + PEg + PEs + PEE

Energy To give something PE you must do work (apply force over a distance) on the something (raising up in g-field) For PEE to occur a FE must be applied by either An E-Field (uniform) A pair of charges

Energy Uniform E-field B A Line Color Red: E-Field Black: Equipotential lines Blue: charge displacement

Energy Pair of Charges

Electric Potential Any point in an electric field is said to have Electric Potential, V. However, only a Difference in PE is measurable (remember zero point) so we talk of electric potential difference AKA potential difference, ΔV.

Potential Difference

Potential Difference

Potential Difference Back to the zero point A convenient zero point to chose in a circuit or any electric system is the “ground”

Battery (cells) A battery produces electricity by transforming chemical energy into electrical energy

Battery Carbon Electrode + Zinc Electrode Sulfuric Acid

Capacitor A capacitor is a storehouse of charge and energy that can be reclaimed when needed for a specific application A capacitor will only charge to the potential difference between the terminals of the battery

Capacitance Capacitance, C: The ability of a conductor to store energy in the form of electrically separated charges Capacitance is the ratio of charge to potential difference

Capacitance Capacitance depends on size and shape

Capacitor Energy stored in a capacitor

Electric Current Movement of electric charge Rate of charge movement

Charge Movement

Charge Movement

Circuit Analogy

Types of Current AC  Alternating current  charges continuously change direction forward and back at 60 Hz Example: outlets (approx 120 V) DC  Direct current  charges move in one direction Example: batteries AC-DC Debate births the Electric Chair

Resistance Resistance is the impedance of the motion of charge through a conductor The ratio of potential difference across a conductor to the current it carries

Ohm’s Law

Resistance Depends on: Length, cross sectional area, material, and temperature

Resistance and Temp

Resistance and Thickness

Resistor An electronic element that provides a specified resistance. A current or voltage REGULATOR

Power (it’s Electric!) Power: Rate at which work is done. OR Rate at which energy is transformed Electric Power: The rate at which charge carriers convert PEE into non-mechanical energy

Reading and Homework Read Chapter 17 HW due on test day: pp 593 - 625 HW due on test day: p 599 1-3; p 601 2, 3, 5-9; p 607 1 – 4 (B); p609 1 – 5 p 615 1 – 6; p 616 2-4, 7,9 p 621 1 – 5 Extra Practice p 626 – 628 11, 20 – 54