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Rad exposure 1613
| Question | Answer |
|---|---|
| formula of WEIGHT | mass x gravity (Newtons; Pounds) |
| formula of DENSITY | mass/volume (kg/m^3) |
| formula of CELCIUS | 5/9 x (F-32) |
| formula of FARENHEITS | (9/5 x C) +32 |
| what is an absolute zero? | -273 C or 0 K |
| VELOCITY formula | d/t (m/s; miles/hour) |
| ACCELERATION formula | the change in velocity / time a=(Vf-Vo)/t (m/s^2) Vf = final velocity; Vo = original velocity |
| FORCE formula Newtons Second Law of Motion | m x a (kg m/s^2 = Newton) |
| WORK formula | F x d (kg m^2/s^2 = Joules) |
| POWER formula | P=W/t (kg m^2/s^3 = Watts) |
| PE formula Potential Energy | PE= m x g x h (Joules) m-mass; g-gravitational constant; h-height |
| KE formula Kinetic Energy | KE= 1/2 (m x v^2) (Joules) m-mass; v-velocity |
| WAVE EQUATION formula | C = wavelength (Angstrom) x frequency (Hz) c = 3 x 10^8 m/s |
| 1 Angstrom = how many meters? | 1 A = 10^-10 meters |
| the Law of Conservation of Energy | E=mc m-mass; c-speed of light (constant: 3*10^8 m/s) |
| Plank's Particle Theory | E= h x v e - energy of photon (eV); h (Planks constant)=4.15 x 10^-15 eVs v-frequency (Hz) |
| how many Joules is 1 eV? | 1.6 x 10^-19 Joules 1eV=energy of 1 electron passing through the potential difference of 1 Volt |
| maximum number of electrons in each shell | 2n^2 K=2; L=8; M=18; N=32 |
| mass of proton and neutron | 1.67 x 10^-27 (kg) 1 (amu) |
| mass of electron | 9.1 x 10^-31 (kg) 1/1837 (amu) |
| definition of isotope | An atom that has gained or lost neutrons from its natural state is called an isotope Hydrogen – 1 proton and 0 neutrons Deuterium – 1 proton and 1 neutron Tritium – 1 proton and 2 neutrons |
| Octet rule | Atoms like to have 8 electrons in the outermost shell (except the K-shell) |
| “valence” of an atom | The number of electrons in an atoms outermost shell determines its ability to bind with other atoms |
| Three fundamental units of physics: | - length - mass - time |
| what is definition a MASS? | Mass is the quantity of matter contained in an object Standard unit: kilogram or gram (Pound or dyne) |
| what is definition of WEIGHT? | Weight is the force that gravity is pulling on a mass. Standard unit: Newton (pounds) |
| First Law of Newton | A body in motion will remain in motion while a body at rest will remain at rest unless a force acts upon it. |
| Third Law of Newton | For every action there is an equal and opposite reaction |
| Boiling point of water | 100 C or 212 F |
| Area of a circle | A=3.14 x r^2 |
| Circumference of a circle | c=2 x 3.14 x r |
| Electrostatics | Electrostatics is the branch of physics that deals with stationary electrical charges |
| What give an object an electric charge? | A differing number of electrons and protons will give an object an electrical charge |
| unit of electrical charge? | coulomb (C) |
| Laws of Electrostatics | 1. Repulsion / Attraction 2. Inverse Square Law 3. Coulomb’s Law 4. Distribution 5. Concentration 6. Movement |
| Coulomb’s Law | F = (k q1 q2)/ r2 F = electrostatic force in Newtons k = 9 x 109 N m 2/C2 q = charges in coulombs r = distance between the objects in meters |
| Inverse Square Law | - the force of attraction or repulsion between two objects is inversely proportional to the square of the distance between them |
| Distribution | - electrical charges reside on the external surface of conductors and are equally distributed throughout non-conductors |
| Repulsion / Attraction | - like charges repel, unlike charges attract |
| Concentration | - the greatest concentration of charges is on the surface where the curvature is sharpest |
| Movement | - only negative charges (electrons) move along a conductor |
| 3 methods of electrification of an object | 1) friction 2) contact 3) induction |
| Friction | - the removal of electrons from one object by rubbing it with a different object - both objects are neutral - the simplest and most fundamental method of electrification - most likely during cold and low humidity conditions |
| Contact | - when a charged object touches an uncharged object, the second object acquires the same charge as the first - a negatively charged object (excess of electrons) will give electrons to a neutral object – it gains a negative charge |
| Induction | - strongly charged object (A) will influence charges of weakly charged/uncharged object (B) w/o phys. contact - charges will be induced to move withinB; when object A is removed, object B will return to its norm. state -can only occur within a conductor |
| “electric field” | Surrounding every charged body is a region in which a force is exerted on another charged body |
| Definition of conductivity | The ability of a material to allow the free flow of electrons |
| Conductors | have a relatively free flow of electrons (little heat is lost) Ex: copper, gold, silver, aluminium |
| Non-conductors or insulators | do not allow electrons to move freely Ex: plastic, rubber, glass |
| Semiconductors | can be either conductors or insulators Ex: silicon, germanium |
| Superconductors | have no resistance to the flow of electrons Ex: ceramics, titanium |
| Three conditions that will allow a current to flow: | 1) in a vacuum 2) in a gas 3) in a metallic conductor |
| A circuit | is the path over which the current flows |
| A source of electrons | 1) battery (DC) 2) generator (AC) |
| Three factors characterize a simple circuit: | 1) potential difference 2) current 3) resistance |
| Potential difference also termed emf (electromotive force) | the difference in electrical potential energy between two points in a circuit |
| Volt | is a unit for potential difference (V) - 1 volt is 1 joule of work done on 1 coulomb of charge - is the potential difference that will maintain a current of 1 ampere in a circuit whose resistance is 1 Ohm |
| Current | - the amount of electrical charges flowing per second - electrons / second - unit: ampere (A) or milliampere (mA) |
| 1 ampere | 1 ampere is 1 coulomb of charge flowing per second - 1 amp = 1 coulomb/second - 1 coulomb = 6.3 x 1018 electrons 1 amp = 6.3 x 1018 e- / second |
| Resistance | - anything that opposes or hinders the flow of electrical current - unit: Ohm - resistance is inherent (within the conductor) and added (load) |
| Inherent resistance (iR) in a wire is dependent upon: | 1)material (conductor–low R; insulator–high R; semiconductor–intermediate;superconductor–no R) 2) length of wire (the longer the wire,more R) 3) cross-sectional area ( the greater the area, less R) 4) temperature ( the greater the T, greater R) |
| RESISTANCE formula | R = p (L/A) R = resistance p (rho) = resistivity coefficient L = length A = cross-sectional area |
| POWER RULE formula | P = IV (Watt) 1 watt is one ampere of current flowing through one volt per second |
| LOSS OF POWER formula | P = I2R I - current in amp |
| Simple Electric Circuit components | 1) Source (battery) 2) Conductor 3) Resistance or load 4) Switch 5) Voltmeter 6) Ammeter 7) Capacitor |
| Ohm’s Law | The mathematical relationship between current, potential difference, and resistance in a circuit: I = V/ R I = electrical current in amperes (A) V = potential difference in volts (V) R = resistance in ohms () |
| What does voltmeter measure? | The voltmeter measures potential difference and is placed in parallel either around the resistance or the source |
| What does the ammeter measure? | The ammeter measures current and is placed in series anywhere on the circuit |
| What does a capacitor do? | It stores electrical energy |
| What is a generator? what are the 2 main parts of generator? | A generator is a device that converts mechanical energy to electrical energy by means of electromagnetic induction Two major parts of a generator: 1) the field magnet 2) the armature (conductor) |
| What does the armature do? | The armature moves (mechanical energy) through the magnetic field that induces current in the armature |
| sources of mechanical energy: | - steam turbine - water (hydroelectric power) - nuclear energy - gas/coal/oil - wind - solar |
| How does Simple generator work? | the field magnet provides magn. field; armature moves through the mag.c field; armature attached to slip rings;carbon brushes allow the slip rings to stay in contact with the wire to the load. AC is generated. 1 cycle is one full rotation of the armature |
| Resistance in an alternating current circuit: | 1) inherent resistance (same as in wire) 2) inductive reactance (R caused by the magnetic field expanding and contracting over its own conductor) 3) capacitive reactance (R caused by the change in polarity of a capacitor in the circuit) |
| “Impedance” (Z) | The total apparent resistance in an AC circuit (a combination of the three) |
| Ohm’s Law for AC | I = V/ Z |
| A direct current (DC) generator | uses “commutator rings” instead of slip rings It produces pulsating direct current |
| A motor | converts electrical energy to mechanical energy Passing a current through a conductor that is inside a magnetic field will create motion in the conductor |
| To determine the direction of the motion induced in the conductor, use | Fleming’s Left Hand Motor Rule |
| Two basic types of motors: | 1) direct current motors (basically the opposite of a direct current generator) 2) alternating current motors a) synchronous motors b) induction motors |
| Synchronous AC motors | - the motor turns at the same speed as the incoming current (60 cycles per second) - they are used in clocks and some x-ray exposure timers |
| Induction AC motors: | - two basic parts: 1) stator ( bars of copper around an iron core) 2) rotor (pairs of electromagnets arranged around the rotor) |
| Ferrous materials: | 1) iron 2) nickel 3) cobalt |
| Classifications of magnets | 1) natural: lodestone (iron oxide or magnetite - Earth) 2) artifical permanent: alnico, steel 3) electromagnet - a magnet created by placing a piece of iron in a coil of current-carrying wire. it is only a magnet when the current is flowing. |
| 3 Laws of Magnetism: | 1) every magnet has two poles: north and south 2) like poles repel and unlike poles attract 3) the force of attraction or repulsion follows the Inverse Square Law |
| magnetic domains (dipoles) | Groups of atoms with their magnetic fields in the same direction 1 domain ~10^15 atoms A ferrous material has lots of domains, but they are in different directions Non-ferrous materials do not have domains, so they are unaffected by a magnet |
| How is a magnetic field created? | when a charged particle (an electron) is in motion or spinning, mag field is created |
| What is a magnetic field? | The area of influence surrounding a magnet is called the magnetic field. The field is made up of lines of force (LOF) or flux lines. The stronger the magnet, the closed together the flux lines are |
| What is a field strength of a magnet? | Field Strength is the number of flux lines (or lines of force) Measured in Webers (Wb) 1 Wb = 10^8 flux lines |
| Flux density? | Flux Density is the number of flux lines per square meter Flux Density = field strength/area Measured in Tesla (T) or Gauss (G) 1 Tesla = 1 Wb/m2 1 Tesla = 10,000 Gauss |
| Flux density of earth? MRI? | The Earth = .5 G or .00005 T A household magnet = .1 T MRI = .5 to 3 T |
| Characteristics of flux lines: | 1) outside magnet,flux lines go from N to S 2) inside magnet, from S to N 3) fl repel when they go in same direction; attract when they go in opposite directions 4) the mag. field is distorted by a ferrous object, but unaffected by a non-ferrous object |
| Magnetic induction | if a ferrous object is placed into a magnetic field, it temporarily becomes a magnet - some materials have the ability to retain their magnetic characteristics (they can become artificial permanent magnets) |
| Magnetic permeability | is the ease that a material becomes magnetized or de-magnetized |
| Magnetic retentivity | is the ability of a material to retain its magnetism |
| Classifications of the Magnetic Properties of Matter | 1. Ferromag. ( high mag. perm.; attracted by mag.): iron, nickel, cobalt 2. Paramag. (low perm.; weakly attracted.):platinum, Al, gadolinium 3. Non-mag. (no perm.;not affected): glass, plastic, wood. 4. Diamag. (weakly repelled): beryllium, bismuth, lead |
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