Electricity

Electric Charge and Force  Electric Charge- electrical property of matter that creates a force between objects. Charges- 2 charges generated by a build-up of electrical charge: positive (+) and negative (-). Like charges repel and opposite charges attract.

Net charge- The total amount (sum) of charge on an object.  When the + and – charges are equal, there is no net charge. Whenever there is an imbalance in the # of + & e-, you have a net electrical charge.  The difference in the number of + & e- is the electrical charge value. + charged objects have more protons, - charged objects have more e-.

The Coulomb, C- the SI unit for electrical charge is the coulomb (1.6 x ). e- & + have exactly the same amount of charge: + =1.6 x =1.6 x e- = -1.6 x  Because the amount of charge on an object depends on the # of + & e-, the net charge of a charged object is ALWAYS multiplied by 1.6 x C

 Conductors & Insulators-  Conductors always allow charge to flow.  Insulators restrict or limit the flow.  Objects can be charged by the transfer of e - s. Electrons transfer easily from one atom to another, thus they can transfer from one material to another. This can occur with or without friction (rubbing). Think of rubbing a balloon on your head, then getting a balloon to stick to the wall.

 Electric Force- force generated by the repulsion/ attraction between two or more charged objects. It also holds atoms together and other molecules. Without it… life would be impossible.  Electrical force depends on charge and distance of objects. The more charge each object has the stronger the electrical force. The further away the objects are, the weaker the electrical force becomes.

 Electrical force acts through a field. An electric field is generated around a charged object due to its charge. (electric field lines leave + charged particles e.f.l. are attracted to – charged particles.)  E. F. L.- point in the direction of the electric force and help define the electric field. ELECTRIC FIELD LINES NEVER CROSS! Positive electric field lines repel each other. The # of field lines reflects/indicates strength of charge.

Current  Voltage and Current  A. Electrical potential energy: Potential energy of a charged object due to its position in an electrical field.

 Potential difference: is the charge of the electrical potential energy per unit of time.  occurs as a charge moves from one place to another in an electrical field. Voltage -SI units for potential difference measure in volts, V -equal to one joule per coulomb (1J/C).  voltage exists across the terminals of a battery (1.5 V to 12 V). These batteries are called cells.  Current - the rate that electric charges move through a conductor.

 Electrical Resistance  A. Resistance: the ratio of the voltage across a conductor to the current it carries. In other words how much electric power can it carry?  Resistance formula:  Resistance = voltage/current or R= V/I.  Units ohm Ω  B. Conductors have low resistances.  C. A resistor is an insulator, any material or solution that does not allow the flow of electrons. In other words they have high resistance

 Circuit symbols and Circuit diagrams