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# AET Study Guide

### DC Terms

Question | Answer |
---|---|

Direct Current | Flow of electrons in one direction throughout a circuit with constant voltage and current. Direct current is caused by a constant difference of potential, both negative and positive. |

Electron | Negatively charged subatomic particles that are loacated and travel around (orbit) the nucleus in an imaginary sphere or shell at the speed of light (186,000 miles/second). Electrons are involved in the conuction of electricity. |

Proton | positively charged subatomic particles that exist within the nucleus of all atoms. Protons are not involved in the conduction of electricity. |

Neutrons | Neutral subatomic particles that exist within the nucleus of all atoms. Neutrons are not involved in the conduction of electricity. |

Conductor | Common building block of electrical circuits that easily permits the movement of electrons from an electrical source to a load and back to the electrical source with a minimum of resistance. |

Resistance depends on what factors? | Resistance depends on such factors as cross sectional area, length, tempature, and conductor material. |

Insulator | Material or device used to prevent the passage of heat, electricity, or sound from one medium to another. |

Static Electricity | Electrical charge that may be built up on a non-conductive surface by friction. Static electricity serves no useful purpose. |

Current | Flow of electricity. Electrical current is the rate of flow of electrons that pass a given point in a specific amount of time. |

Coulomb | Basic unit of electrical quantity. a coulomb is equal to 6.28 billion-billion electrons (6.28 x 10 to the 18th) |

Ampere (A,amp) | Unit of measure used to express the flow of electrons (current). One amp is the amount of current that can be forced through one ohm of resistance by the pressure of one volt. Current is represented by the international symbol "I" |

EMF (E) | Electron moving force measured in volts. EMF is the force causing electrons to move through a conductor. |

Volt (V) | Basic unit of electrical pressure. A volt is the amount of force required to cause one amp of current to flow through on ohm of resistance. Volt is often expressed by such terms as voltage, voltage drop, potential difference, EMF, or IR drop. |

Resistance (R) | Electrical characteristic of a conductor. Opposition that is presented to the flow of electricity. Resistance is the force that opposes or slows down another force, drops voltage, and consumes power. Resistance is measured in ohms. |

Ohm's Law | Ohm's Law states that "the amount of current flowing in a circuit is directly proportional to the circuit voltage and inversely proportional to the circuit resistance." |

Ohm (Ω) | Unit of electrical opposition to the flow of current. A circuit has one ohm of resistance when it limits the flow of current to one amp under a voltage pressure of one volt. |

Watts (W) | basic unit of power that is the product of voltage multiplied by current. One watt (1/746 horsepower) is the power produced in a circuit that has one amp of current flowing under a pressure of one volt. |

Capacitor | Electrical component used to store electrical energy in the form of an electrostatic field. A capacitor is a device made of two parallel conductors separated by an insulator. |

Working voltage | Maximum amount of DC voltage that can be safely appled across a capacitor. |

Inductor | Coil or other devise used to introduce inductance into a circuit. An inductor is a winding, or coiling, of multiple turns of wire. |

Battery | A device made of one or more individial electrochemical cells used to store chemical energy and make the energy available in the electrical form. There are two categories of batteries, primary and secondary. Batteries can store DC power. |

Left-hand Rule | Refers to generators. This rule is for determining the direction of movement of a current-carrying conductor in a magnetic field. |

Magnetism | Ability of a magnet to attract certain materials containing iron and to influence electrons. Magnetism is the principal way to effectively produce AC electricity. |

Magnetic Permeability | Measure of ease that lines of flux travel through a material. |

Scientific Notation | Short way of expressing a given number as a number between 1 and 10 multiplied by 10 to the appropriate power. |

Metric Prefixes | Measurements relating or using the metric system of measurement. |

Henry (H) | Basic unit of measurement for inductance. One Henry is the amount of inductance a current change of one ampere per second induces a voltage of one volt. |

Farad | Basic unit of capacitance. One farad holds one coulomb under pressure of one volt. |