Electric Fields and Potential Physics Chapter 33

Engagement Why is wiring covered with rubber? Use the terms conductor and insulator in your explanation.

Agenda Review HW Note taking Class work Q and A Closing

Electric Field Space around every charge Has magnitude and direction* Magnitude – how strong Direction- its response to a (+) charge

Electric Field Lines Express electric field with vectors Length of line = strength Direction of arrow = response to (+) charge

Check for Understanding Why are the field lines drawn away from the (+) charge and toward the ( - ) charge?

Electric Potential Energy Energy of a charged based on location Exertion of work by an external force adds potential energy to object

Electric Potential Energy Moving from A to B Moving the (+) test charge from location A to B requires work b/c goes against E therefore increases in PE of charge Moving the (+) test charge from location B to A is in the direction of the electric field so PE decreases since no work needed Moving from B to A

Electric Potential Energy Moving from A to B Moving the (+) test charge from location B to A requires work b/c goes against E therefore increases in PE of charge Moving the (+) test charge from location A to B is in the direction of the electric field so PE decreases since no work needed Moving from B to A

Electric Potential Different from electric potential energy The electric potential energy per charge Units are volts (V) Often called voltage

Check for Understanding What is the difference between voltage and electric potential? Nothing, they are the same thing.

Reach for the Stars MeasurementSymbolUnits Electric potential VV (volts) Electric potential energy PEJ (Joules) ChargeqC (Coulombs) 1 volt = 1 joule coulomb

Understanding Electric Potential or Voltage 1 volt = 1 J of energy per coulomb charge 1000 volts = 1000 J of energy per coulomb charge High voltage DOES NOT mean danger *high voltage requires high energy and a lot of charge. *Often very little charge is involved; therefore, little energy is required and the electric potential/voltage is small

Class work / Homework Make sense of all these terms. Consider rubbing the balloon on your hair and it sticking to the wall. Explain how this works, using the following terms/ideas 1.Charge by friction 2.Charge by polarization 3.Electric potential energy 4.Electric potential 5.There is voltage but very little Use the notes and chapter 32 and 33 in the book to help.

Closing In order for a particle to have voltage, what must the particle have? Draw the electric field around the charges + _