Presentation on theme: "Chapter 5 Electrostatics"— Presentation transcript:
1 Chapter 5 Electrostatics Photon EnergyPhoton energy is DIRECTLY proportional to its frequencyPhoton energy INCREASES as wavelength DECREASESPhoton energy INCREASES as kVp INCREASES
2 Electricity, Magnetism and the x-ray tube relationship Primary purpose of an x-ray tube is to convert electric (A/C current) into ELECTROMAGNETIC ENERGY!
3 Laws of electrostatics Unlike charges ATTRACTLike charges REPELElectrostatic force is DIRECTLY proportional to the PRODUCT of the charges and the SQUARE or the distance between them (kind of like Inv. Sq. law and laws of magnetics)When objects are “electrified, the charges are distributed throughout the object – BUT are greatest at POINTED spots
4 Electric Terms Electrodynamics – electron flow Conductors – Matter that conducts the currentInsulators – Matter that INHIBITS current flowSUPERCONDUCTOR – Like an MRI unit – low resistance (niobium/titanium)Semi-conductor = depending on the conditions, can be either a conductor/insulator
5 Electronic Terms, con’t Electric Potential = Volt (V)Resistance = Increasing electric resistance (Ohm’s) = LESS current flow in amps (A)Ohm’s Law = voltage across the circuit is equal to the CURRENT X RESISTANCE (V + IR) where I= current (amps), R= resistance in ohm’s, V= POTENTIAL in voltsWATT (W) = measurement of electrical power
6 Current Direct Current (DC) = electron flow in only one direction Alternating current (AC) SINUSOIDAL form each way (+ & -)Magnetism and AC are very closely related (+/- OR N-S pole charges)Magnets are classified according to their origin (natural, permanent, electromagnet)
7 Magnetic Laws Every magnet has TWO poles Like poles REPEL, unlike ATTRACTMagnetic lines are ALWAYS closedMagnetic force and the DISTANCE from the magnet are INVERSLEY proportional to the square of the distance – BUT the attraction is GREATEST at the POLES rather than the sides of the magnet.
8 4 Fundamental forces of nature GravityStrong nuclear forcesWeak nuclear forces/interactionElectromagnetic force(s)
9 The BatteryDiscovered (invented) by “Volta” who made a “voltaic “ pile (copper, zinc and wet paper) = 1st crude batter and SOURCE of EMF!
10 Charges in motionCan create a magnetic field (flux lines, gauss, tesla)The book takes a lot of time with the “right hand rule” spend your time on other items:Solenoid – coil of wire that MAGNIFIES the action of the current flow via COILSElectromagnet – ferromagnetic material wrapped in a coil of wire
11 FARADAYFound that a coil of wire & a mangetic field that is MOVING can cause current (AMPS) to flow in the wire coil – INDUCTION OF CURRENT – Farady’s lawMagnitude of induced current depends on:Strength of magnetic fieldVelocity of the magnetic field as it moves past the conductor (coil)ANGLE of the conductor (coil) to the magnetic fieldNUMBER of TURNS in the conductor
12 LENTZ’ LawInduced current flows in a direction such that it opposes the action that induces itTwo ways to induce current:Self induction – single coil of wire with a current running through it – OPPOSES the magnetic forces it producesMutual induction – inducing a current flow through a secondary coil by passing a varying current through the primary coil – VERY IMPORTANT FOR TRANSFORMERS!
13 Electric GeneratorSimple electric generator: coil of wire placed in a strong magnetic field between tow poles of a magnet
14 Electric MotorElectric energy applied to the “current loop” to produce a mechanical motion – rotation of the loop in the magnetic field – like the stator windings on the x-ray tube – able to have the anode turn w/o any current on the inside of the tube – INDUCTION motor
15 TRANSFORMERSChange the intensity of the AC voltage and current by MUTUAL INDUCTIONVoltage and AMPS may be changed (stepped up or down) by changing the numbers of coils on each side of a transformer
16 Transformer Energy Losses Resistance to current = heat lossAC reversal currents = hysteresis (self induction current flow opposes magnetic field)Magnetic current fluctuation from + to - = “Eddy currents”
17 Types of TransformersClosed coreAutotransformerShell type