click below
click below
Normal Size Small Size show me how
PHYSICS test 5..
| Electrostatics | the study of electricity at rest. |
| Atoms | Every atom is composed of a positive nucleus surrounded by negative electrons. |
| What are the 4 fundamental forces? | Strong, Electromagnetic, Weak, and Gravity |
| Coulomb | Unit for charge |
| Electrical Force | Decreases as distance increases |
| Robert Millikan | First person to find the charge of an electron |
| Conservation of Charge | Electrons cannot be created or destroyed, just transferred. |
| Charging | Occurs when when transferring electrons from one place to another |
| Two ways charging can be done | Induction and contact |
| Contact Charging | When material rub together, electrons can be transferred. |
| Charge Polarization | When a charged object is brought near an insulator, there are no free electrons to migrate.Instead there is a rearrangement of charges within the material.Example: balloons |
| Induction Charging | This occurs when an object is brought close to a charge and then grounded or separated. |
| Conductor | A material that allows electrons to flow freely is a good conductor of electricity |
| What is the best conductor | Silver, copper is also good, and cheaper |
| Insulator | A material that doesn't allow electrons to flow Examples: glass, air, wood |
| Semiconductors | Can be made to behave like both conductors and insulators |
| Superconductors | Allow zero resistance to the flow of charge. Once the flow starts, no energy is lost to heat. Extremely cold temps are required |
| Electric Potential | It takes energy to push a charged particle against an electric field. Also known as voltage. |
| Electric Storage | Capacitors can store charges after the current has stopped and be discharged when a conductive path is provided. |
| Van de Graff Generator | Positive charges are built up on the metal sphere and discharge when brought close to the small negative sphere. |
| How does lightning work? | The negatively charged clouds induce a positive charge on the Earth’s surface. When enough charged builds, it produces an electrical discharge. |
| Voltage | Electric pressure |
| Current | Charges flowing through a circuit |
| Flow of Charge | Electrons flow from the negative terminal to the positive |
| Resistance | How much current depends on the voltage but also on the electrical resistance. More resistance = less current. |
| What is resistance measured in? | Ohms |
| Ohm's law | current is directly proportional to the voltage in and circuit and inversely proportional to the resistance. V=IR |
| Series Circuit | Current has only 1 pathway Each resistor gets part of the voltage More resistors, more resistance If one device breaks, all current stops |
| Parallel Circuit | Current has more than one pathway Each resistor gets all of the voltage More resistors, less resistance If one device breaks, current continues in the others |
| What causes electrical shock? | Current |
| Electrical Power | The rate at which electric energy is converted into another form. |
| P=IV | Electrical power |
| Direct Current (DC) | Refers to flowing charge in one direction. Example: batteries |
| Alternating Current (AC) | When electrons are moving back and forth. Has a frequency of 60 Hz |
| Oscilloscope | A device used to graph voltages vs. time or other voltages |
| Diode | Only allows current to flow in one direction. Converting AC to DC |
| Capacitor | Stores a charge between two plates |
| How does an LED work? | When the positive of a battery is hooked to the N side, no current flows |
| 4 Natural elements that are magnetic? | Iron, cobalt, nickel and gadolinium |
| Source of all magnetism? | Due to the motion of charged particles |
| Magnetic Fields | The lines from pole to pole surrounding a magnet. Start at north and end at south |
| Neodymium | A rare earth element that can be made into very strong magnets because of its 4 unpaired electrons. |
| Electromagnets | A coil of wires carrying a current. |
| Charged particles | If this is moving through a magnetic field, it deflects. |
| Electrical forces | opposites attract, like forces repel |
| Power | The rate at which electrical energy is changed |
| Fuse | Breaks the circuit if too much current flows |
| What happens when there is a short circuit? | Current will travel through a short instead of through anything that has resistance. |
| Solar Wind | Charged particles flowing from the sun. |
| Magnetic Field | The lines from pole to pole surrounding a magnet. |
| What is the source of magnetism? | Spinning motion of electrons. |
| How does the Earth have a magnetic field and which direction does it flow? | Moving currents of molten iron in the core. It goes from the south pole to the north. |
| What happens when a current travels in a coil of wire? | It induces a magnetic field (electromagnet) |
| Galvanometer | A coli of wires that depending on the voltage deflects a certain amount. |
| Northern Lights | When cosmic rays collapse the Earth’s magnetic field. |
| Generator | Mechanical energy transformed into electrical energy. Uses a coil of wire and a magnet. |
| Transformer | Is used to step up voltages and reduce current so electricity can be transported over long distances. When it arrives another transformer steps it back down. |
| What happens when you move a magnet through a coil of wires? | It induces a short burst of current in the wires. |
| Why did Nikola Tesla invent AC? | Because DC requires high current witch requires larger wires and many of them. Also it cannot be transported long distances. |
| Faraday's Law | An electric field is induced in any region of space in which a magnetic field is changing. |
| Maxwell's Counterpart to Faraday's Law | A magnetic field is induced in any region of space in which an electric field is changing. |