CP Physics

 Space around every electric charge acts as a force field that will interact with other charges  Can only observe a field by watching the forces it produces on other charges  Are storehouses of energy

 Lines of force = lines drawn around a charge to represent the forces experienced in its electric field (are vectors) Stronger fields – have more lines which are close together Weaker fields – have fewer lines which are farther apart

 Lines of force, continued Length of lines indicate amount of force (longer = more force) Direction lines point indicate type of charge  Point toward negative charges  Point away from positive charges Lines show interaction between charges  Lines always drawn from positive charges to negative charges

A – shows electric field around a positive charge B – shows the electric field interactions between a positive charge and a negative charge C – shows the electric field that exists between a positively charged plate and a negatively charged plate

 Charges spread out over a conductor’s surface so that the electric field inside it is zero  True reason car is safest place in a thunderstorm: if hit by lightning, the charges spread out over the car’s surface and inside the car you experience zero electric force

 Energy a charge possesses because of its location (as compared to other charges)  Separating a positive charge from a negative charge – increases potential energy because you must do work against their attraction  Pushing like charges together – increases potential energy because you must do work against their repulsion

 Electrical potential energy per charge  Also known as potential difference (or voltage)  Unit = volt (V) (1 volt = 1 J/C)  Can create large voltages, but if only a few charges, then very low potential energy  High voltages require great amount of energy only if there is a great amount of charged involved (1 C = large amount of charge)

 Found in nearly all electronic circuits  Store electrical energy  Made of two metal plates that store energy from the battery in an electric field between the two plates  Fully charged when voltage equals the battery voltage  Discharges when path provided between plates  Ex. Used in camera flashes

 Device to build up high voltages  Charges move up insulator belt inside generator and move to outside surface – field inside generator is always zero  Charges continuously move up to dome of generator  High electric potential can result