1. Concept Summary Batesville High School Physics

2. Electric Fields  An electric charge creates a disturbance in the space around it - an electric field.  The electric field extends infinitely far but weakens with distance.  This electric field exerts a force on other charges within the field.

3. Electric Fields  Electric fields are vector fields.  Direction at any point is the direction that a positive charge would move if placed there.  Magnitude at any point, E = F/q  Units of E are Newtons/Coulomb  Force a charge feels, F = qE

4. Electric Field Lines  Point in the direction a positive charge would move  Field is stronger where field lines are closer together.  Also called “lines of force”

5. Charged Conductors  If a conductor has a static charge:  All of the charge resides on the surface of the conductor  The electric field everywhere inside the conductor is zero.  If the conductor is not spherical, the charge distribution will not be uniform.

6. Electric Potential Energy  You have to do work to move a charge in an electric field.  The electric potential energy of a charge at a point in an electric field = -(work done by the electric field when the charge is moved there).

7. Electric Potential  Electric potential = electric potential energy per unit charge  Electric potential, V = EPE/q  Units: Joule/Coulomb  1 Volt = 1 Joule/Coulomb  Electric potential is commonly called voltage.

8. Voltage  A location can have a voltage whether or not a charge is located there.  The voltage difference (potential difference) between two points tells you:  The energy available when a unit charge is moved between the points, or  The work that needs to be done to move a unit charge between the two points.

9. Voltage  The voltage between two points (potential difference) tells you the amount of energy 1 Coulomb of charge will lose when it moves between the two points.

10. Storing Electrical Energy  Since unlike charges attract, it takes work to separate unlike charges.  This work is stored as electrical potential energy

11. Capacitors  A capacitor is a device that contains 2 parallel conducting “plates” insulated from each other.  It is used to store electrical energy, by holding positive charges on one plate and negative charges on the other.  Capacitors can be charged to high voltages and store large amounts of energy.

12. Van de Graaff Generator  The Van de Graaff Generator is a device for creating large voltages.  Voltages of 150,000 V + are common

13. Voltage and Danger  ENERGY DOES WORK!  The Van de Graaff gives each charge a large amount of energy (high voltage), but there aren’t many charges - therefore the Van de Graaff delivers very little total energy.

14. Voltage and Danger  An electrical outlet (120 Volts) gives comparatively little energy to a charge, but it can deliver LOTS of charge - at least 15 Coulombs of charge per second.  Therefore, the electrical outlet can deliver LOTS of energy - enough to kill you!

15. The End