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Bushong Ch 5
Electricity and Magnestism
| Question | Answer |
|---|---|
| What does the xray system convert electrical energy into | Electromagnetic energy |
| Electrostatics | The study of stationary electric charger |
| Matter has (3) | Mass, energy equivalence, and electric charge ->Electrons -; Protons + |
| Electrification is created by 3 | Contact, friction, induction |
| Electrification is due to | the movement of negative electric charges |
| Coulomb | (C) The fundamental unit of electric charge |
| Like charges/unlike charges | Like charges repel one another, unlike charges attract |
| Uncharged charges | do not have an electric field |
| Electric charge of a conductor and electrostatic charges are concentrated | On the sharpest curvature of the surface |
| Electric Potential Unit | Volt (V) |
| Electric Current | (Electricity) When electric potential is applied to objects, such as copper wires, when electrons move along the wire |
| Electrodynamics | The study of electric charges in motion. DYNAMIC-MOVING |
| Conductor, and examples 3 | Any substance through which electrons flow easily. Copper is best, Al and h20 good. |
| Insulator, and Examples 5 | Any material that does not allow electron flow. Rubber, plastic, wood, glass, clay |
| Semiconductor | A material that under some conidiots behaves as an insulator and in other conditions behaves like a conductor |
| At room temp, all materials... | resist the flow of electricity |
| Resistance ______, as the temp ______. | Decrease; temp of material decreases |
| Superconducitivty | The property of some materials to exhibit no resistance below a critical temperature |
| Ohms Law | The voltage across the total circuit or any portion of the circuit is equal to the current times the resistance (V=IR) |
| Current unit | Amperes, I |
| Electric resistance unit | Ohm's; R |
| Series circuit | All circuit elements are connected in a line along the same conductor |
| Rules for R, V, I in series | R-add them up, V-add them up, I-stay the same |
| Parallel Circuit | Contain elements that are connected at their ends rather than lie in a line along a conductor |
| Rules for R, V, I in parallel | V-stay the same. I-add them up, R- 1/R=1/R+1/R... |
| Direct current | Electrons flow in 1 direction only |
| Alternating current | AC. Electrons flow alternating in one direction and then the other. Sinusoidal electric waveform |
| Power equation and unit | P=IV; Watts |
| Magnetism is caused by | Any charged particle in motion. A moving charged particle induces a magnetic field in a plane perpendicular to its motion |
| Magnetic field moves... | When a charged particle moves in a circular or ellipitical path, the perpendicular magnetic field moves with the charged particle |
| Lines of magnetic fields | are always closed loops |
| Magnetic diploes in ferromagnetic material | ex. Iron. they are randomly oriented until the diploes are brought under the influence of an external magnetic field |
| Classifying magnets | They are classified according to the origin of the magnetic property |
| 3 Classifications of magnets | Naturally occuring magnets 2. Aritifically induced permanent magnets 3.Electromagnets |
| Ex of naturally occuring magnet | Imaginiary line of force. Gravity. Earth is a prime example |
| Artifically induced permanent magnet, what it is, looks like, and is made of | Lines of forces are undisturbed by nonmagnetic material. Come in many sizes and shapens- usually bar or horseshoe and are made of FE.can be destroyed |
| Example of ariticually induced permanent magnet | Compass |
| Electromagnets | They are deviated by ferromagnetic material. Consist of wire wrapped around an iron core. |
| Magnetic field in an electromagnet is created by. and the intensity | sending electricity through the wire. tbe intensity of the magnetic field is proportional to the electic current |
| Magnetic states of matter 4 | Nonmagnetic, Diamagnetic, Paramagnetic, Ferromagnetic |
| Nonmagnetic, 2 Ex | Unaffected by a magnetic field. Wood, glass |
| Diamagnetic, 1 Ex | Weakly repelled by both poles. Water |
| Paramagnetic, 1 Ex | Weakly attracted to both poles. Gadolonium |
| Ferromagnetic, 3 Ex | Can be strongly magnetized. Iron, nickel, cobalt |
| How magnetic fields flow | the imaginary lines of the magnetic field leave the north pole and enter the south pole |
| Ferromagnetic and nonmagnetic material attractions | Ferromagnetic material attracts magnetic lines of induction, whereas nonmagnetic material does not |
| Magnetic force equation | The magnetic force is proportional to the product of the magnetic poles strengths divided by the square of the distance between. If the distance between 2 bar magnets is halved, the force increases by 4 |
| SI unit for magnetic field strength | Tesla T |
| Electromotive force | Any devise that converts some energy form directly into electric energy is EMF or electric potential |
| Electric potential is measured in | Joule/c or volts |
| Oerstends Expirament | 1820. With no electric current in a wire, the compass points north. with electric current the compass points toward the wire |
| Oersteds findings | An electric current produced a magnetic field. Any charge in motion induces a magnetic field |
| Electron flow and magnets | Electrons flowing through a wire produce a magnetic field. Magnetic field lines form concentric circles around the current carrying wire |
| The loop | Magnetic field lines are concentrated on the inside of the loop. At the very center of the loop, all field lines add together, making the magnetic field strong |
| Increasing intensity of magnets | Stacking more loops on top of each other increases the intensity of the magnetic field |
| Solenoid | A coil of wire |
| Faradays Law | A magnet at rest produces no electricity but if the magnet is moved electric current is induced |
| Faradays law-the magnitude of the current depends on 4 things | 1. strength of manetic field 2.the velocity of the magnetic field as it moves past the conductor 3.Angle of the conductor to the field 4.The # of turns in the conductor |
| Radio reception is based on | The principals of electromagnetic induction |
| Radio emission | It consists of waves of EM radiation. Each wave has an oscillating elecxtric and magnetic field. The oscillating magnetic field induces motion in the electrons in the radio antennae, resulting in radio signal |
| Lenz law | Moving gives induced current BUT direction matters |
| Self induction Ex? | A coil passes a steady and relatively unimpeded direct current but resists the passage of an alternating current |
| What IS self induction | induction of an opposing voltage in a single coil by its own changing magnetic field |
| Mutual indcution | the generation of an AC in a secondary coil by supplying, an AC to the primary coil; which inturn induces a current in the secondary coil |
| AC | Induced current in a simple generator is constant. It varies according to the orientation of the coils wire in the magnetic field. Induced current flows 1st in 1 direction and then in the other. following a sinusoidal pattern |
| Direct current motor | Electric energy is supplied to the current loop to produce a mechanical motion, a rotation of the loop in the magnetic field. The EM current loop is 180. The loop rotates continuously |
| Induction motor | The rotating rotor is still in a seires of wire loops. however the external magnetic field is supplied by several fixed EMs called stators. This powers the anode. |
| The energy is an induction motor is supplied | to the external magnets rather than the rotor windings |
| The transformer and intensity | The transformer changes the intensity of alternating voltage and current by mutual induction |
| The transformer and energy | Doesnt convert 1 form of energy to another but transfers electric potential and current into higher or lower intensity |
| Closed core EM | This produces a closed magnetic field primarily comfined to the core. No ends for the ferrogmagnetic field lines to escape |
| The transformer is used to | to change the magnitude of voltage and current in an AC circuit |
| The change in transformers | Is directly proportional to the ratio of the number of turns in the secondary coil to the number of turns in the primary coil. |
| Transformer law equation | Vs/Vp=Ns/Np. Ns/Np is known as the turns ratio in the transformer |
| Transformers and turn ratios | A transformer with a turn ratio greater then 1 is a step up transformer. less than 1 is a step down. |
| Transformers effect on current. 2 equations | Is/Ip=Np/Ns or Is/Ip=Vp/Vs. In the N equation. If step down 1/#, if up just # |
| Transformer power loses 3 | Resistance, Hysteresis, Eddy Currents |
| Resistance is | electric current in the copper wire |
| Hysteresis is | The alternate reversal of the magnetic field |
| Eddy current | Found within the magnet. These currents oppose the magnetic field that induced them |
| Autotransformer consists of | An iron core with only 1 winding of wire. The single winding acts as the primary and secondary |
| Autotransformers are based on | self induction not mutual induction |
| Autotransformers connects at | different points on the coil for both primary and secondary sides. Its restricted to only small step up or step down in voltage |
| Shell type transformer | Two closed cores. More efficient than the closed core. Most commonly used transformer |
Created by:
rachelbeatty4
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