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Bushong Ch 5

Electricity and Magnestism

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