Transcript Slide 1
Voltage & Current Overview ● ● ● ● Atoms / Electrostatic Force Voltage / Electromotive Force Current Conductors and Insulators Atoms ● Atoms are the smallest unit of an element. Atoms are comprised of electrons, protons, neutrons and a nucleus. Different arrangements of the particles within an atom determine what type of element it is (hydrogen, oxygen, silicon, arsenic, etc.) - - - + + + - - Atoms ● Proton: A proton is a positively charged particle. A proton lives inside the nucleus. Protons give an atom its mass (a proton weighs 1,840 times more than an electron). ● - - + ++ - Electron: An electron is a negatively charged particle. An electron spins in orbit around a nucleus because it is attracted to the protons inside. Understanding this concept is the key to understanding electricity. Electrostatic Force ● The reason electrons are attracted to protons is called electrostatic force. Electrostatic force is the principle of attraction and repulsion of charges. Law of Electrostatic Force ● Unlike charges Attract + ● - Like charges Repel - - Voltage ● Potential Difference / Electromotive Force Potential difference, or voltage, is defined as “The difference in potential between two charged objects which provides the force to move electrons”. A charged particle with an extra proton or electron is called an ion. Ions want to be neutral, meaning they want a balanced number of electrons and protons. Ions will do whatever is necessary to become neutral. Another name for this concept is 'electromotive force', or EMF. A simple example of EMF is touching a doorknob after shuffling your feet on carpet. A major example is lightning. The symbol for voltage is 'V' or 'E'. E represents 'Energy'. The unit of measurement is volts. VE or Voltage Makers ● We produce voltage by six different methods: ● Friction - ● Pressure - Also called piezoelectricity; Quartz or similar crystals can be Rubbing two different materials together and creating static electricity; very impractical and used little. (Research is ongoing for emerging technology such as charging cellphones w/friction in clothing). used to convert mechanical energy into electrical energy. Used in low voltage applications such as microphones, radio receivers and sonar equipment. ● Heat - Heat generated voltages can be produced by heating the junction of two unlike materials such as iron and copper. Thermocouple is the term for the device that produces voltages using heat. They are widely used to measure temperature and as heat-sensing devices in automatic temperature control equipment. Voltage Makers ● We produce voltage voltages by six different methods: ● Light-The term photoelectricity is used for generating voltage by using light. When light strikes the surface of a substance, it may dislodge electrons from their orbits around the surface atoms of the substance. This occurs because light has energy, the same as any moving force. Some form of the photoelectric principle is used in television cameras, automatic manufacturing process controls, solar calculators, and intrusion detection alarms. ● Chemical Action - Voltage may be produced chemically when certain substances are exposed to chemical action. Another word for producing voltage by chemical action is electrochemistry. An ordinary battery, either wet or dry, produces voltage by chemical action. ● Magnetism-Current flows when you subject electrons to the force of a magnetic field. Magnetism is the most popular way to generate electricity today. Almost all electric power stations operate by producing magnetism-generated electricity. Current ● CURRENT is the flow of electrons from a (-) potential to a (+) potential. The letter reference designator is I. The use of the letter I for current represents the intensity of the charge of motion ► The unit of measure for current is Ampere or Amp - ● Flows from negative (more electrons) I ++ ● Flows to positive (less electrons) Conductors ● A conductor provides a path for electrons to move through. The following materials are good conductors: ● Silver ● Copper ● Gold ● Aluminum Voltage can move electrons through these materials with minimum opposition or resistance. Insulators An insulator is a material that blocks current flow. The following are good insulators: ● ● ● ● ● Rubber Plastic Ceramics Glass Paper We use insulating materials to cover wires which carry electricity. Electrical Circuit ● Below are the three items needed to make a basic electrical circuit. ● Voltage Source - The force that causes electrons to move. ● Conductor - Current flows through the conductor. Conductors deliver the current to the load. ● Load - Electronic device that requires electricity to perform work for you Electrical Circuit Conductor Voltage Source - Load + Conductor Summary ● All materials are made up of tiny "building blocks" known as atoms. ● Electrons have a negative (-) electric charge. ● Protons have a positive (+) electric charge. ● Law of Electrostatic Force states: unlike charges attract and like charges repel. ● Potential Difference / Electromotive Force = Voltage The difference in potential between two charged objects which provides the force to move electrons. Summary ● We produce voltage by six different methods: friction, pressure, heat, light, chemical action and magnetism. ● CURRENT is the flow of electrons from a (-) potential to a (+) potential. ● Conductors provide a path for electrons to move through. ● Insulators are made of materials that block current flow. ● Electrical Circuits exist when voltage forces current to flow from a (-) potential through a circuit load to a (+) potential. Voltage & Current