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Ch.5 MAGNETISM ELECTROMAGNETISM

Ch.5 MAGNETISM ELECTROMAGNETISM. Magnetism. When charged particles moves a magnetic field is induced Every moving charges produces a magnetic field. MAGNETS. USUALLY MADE OF IRON EVERY MAGNET HAS A NORTH AND SOUTH POLES LIKE SIMILAR CHARGES REPEL OPPOSITES ATTRACT.

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Ch.5 MAGNETISM ELECTROMAGNETISM

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  1. Ch.5MAGNETISM ELECTROMAGNETISM

  2. Magnetism • When charged particles moves a magnetic field is induced • Every moving charges produces a magnetic field

  3. MAGNETS • USUALLY MADE OF IRON • EVERY MAGNET HAS A NORTH AND SOUTH POLES • LIKE SIMILAR CHARGES REPEL • OPPOSITES ATTRACT

  4. Demonstration of magnetic lines of force with iron filings • NORTH & • SOUTH POLES

  5. TESLA –measurement of magnetic strength - used in MRI

  6. FERROMAGNETIC • OBJECTS THAT CAN BE MAGNETIZED by exposure to a magnetic field. • (IRON, COBALT, NICKEL) • 3 TYPES OF MAGNETS • LODESTONE – NATURAL (PERMANENT) • ARTIFICAL – N & S INDUCED • ELECTROMAGNET – temporary magnets produced by moving electric current

  7.  Ferromagnetic material such as iron attracts magnetic lines of induction, whereas nonmagnetic material such as copper does not.

  8. A moving charge creates a magnetic field • When a charged particle is in motion – a magnetic force field perpendicular to the motion is created • In Electromagnetism – movement of e- in a electric current creates an electric field

  9. Current flow direction of thumb – Magnetic filed – fingers An electric current is considered to be a + flow The negatively charged electrons are moving in the direction opposite to the current flow RT HAND RULE

  10. RT HAND RULE • Direction of magnetic current lines • When wire is looped – magnetic field is strengthened = 2x more • Adding more loops – increases strength • Magnetic lines curve around to other pole

  11. When the wire that is conducing the current is looped • The magnetic field is strengthened • It is now 2x as strong • The MORE the LOOPS – • The STRONGER the field

  12. TRANSFORMER PRINCIPLE INCREASE # OF COILS OF WIRE • INCREASES THE VOLTAGE

  13. ELECTROMAGNETIS CREATED BY: • SOLENOID: Current flowing through a wire coil of wire • Putting a magnet in the middle of the coil of wire increases the strength if the electromagnet’s magnetic field

  14. A coil of wire is a helix • Supplied with current it is a solenoid • Add an iron core – simple form of • ELECTROMAGNET

  15. HOWELECTRIC & MAGNETIC FIELDS INTERACT Faraday discovered that the magnetic lines of force and the wire must have a motion relative to each other to induce an electrical current

  16. ELECTROMAGNET INDUCTION • Moving a wire through a magnetic field will induce a current (Faraday) • Wire or field can move • Moving a magnet through a coil of wire will induce an electrical current

  17. “Faraday’s Laws : or how to increase the strength of the induced current • Increase the Strength of field or size of magnet • Increase the SPEED of motion • Change the ANGLE (more perpendicular) • Increase the Number of Turns of coil

  18. MOVING A BAR MAGNET THROUGH A COIL OF WIRE WILL INDUCE A CURRENT TO FLOW THROUGH THAT WIRE ELECTROMAGNET INDUCTION

  19. INCREASING VOLTAGE • Increasing the number of coils of wire will increase magnetic field strength – • Increasing the number of coils moving in a magnetic field will increase the voltage induced • Doubling the # of turns of wire = Doubles the Voltage

  20. INCREASING CURRENT • Increasing the strength (size of bar) of the magnetic field will increase the current • Increasing speed of motion through wires will increase current

  21. Increasing Current • 2 turns of coil and moved 1 / sec • 4 turns of wire (2x more) and moved 3/sec • How much stronger is current? • 2 x 3 = 6 times stronger

  22. Angle of motion • Motion of the wire perpendicular to the magnet (magnetic field) produces more current than a magnet that is at an oblique angle

  23. AC – magnetic field moves in and out

  24. Faraday’s law ? Regulate the strength of the induced current BY INCREASING: • _________of the Magnet • _____________ of the motion • _____________ of the magnet • ____________ on the conduction coil

  25. Faraday’s law Regulate the strength of the induced current • Strength of the Magnet • Speed of the motion • Angle of the magnet • Number of turns on the conduction coil

  26. MUTUAL INDUCTION • Occurs when 2 coils of wire are placed close together • Varying current supplied to first coil • Induces a similar flow in the second coil

  27. What part of the circuit board does this look like?

  28. MUTUAL INDUCTION(STEP UP & DOWN TRANSFORMERS)

  29. SELF INDUCTION • SIMILAR TO 2 COILS WRAPPED ON ONE CORE • (Self induction occurs in single coil of wire – the flow of electrons in one direction produces a current (in the same wire) – then when flow of current changes – polarity of magnet changes)

  30. . What is responsible for supplying a precise voltage to the x-ray machine?

  31. . What is responsible for supplying a precise voltage to the x-ray machine? THE TRANSFORMER

  32. AUTOTRANSFORMER

  33. Transformer Design pg 95 Closed core (open) auto Shell type

  34. TRANSFORMERS • STEP UP OR DOWN • OPEN CORE, CLOSED CORE OR SHELL TYPE • ABOUT 95% EFFICIENT • AUTOTRASFORMER = _____ induction • Functions to provide ___________ • Both types require AC for operation

  35. A transformer with more secondary windings than primary windings ____. • has a greater secondary voltage • has a greater power output than input • is a step-down transformer • none of the above

  36. All transformers must operate on AC to provide the collapsing magnetic fields that induce the voltage changes in the secondary coil Ideal Efficiency – no loss Reality best = ~95% Loss due to Cu (copper) resistance (Copper loss) resistance to flow in a conductor  (lg) wire diameter will reduce loss Eddy currents Laminating the core reduces eddy loss Hysteresis occurs in the core due to the loss of energy because of constant changing AC current) Improved using silicon core material Transformer Efficiency

  37. A C ELECTRONS SWITCH DIRECTIONS OF FLOW RECTIFIED = DC A LOOP OF WIRE ROTATED IN A MAGNETIC FIELD = PRODUCES A CURRENT – WIRE FLIPS BACK & FORTH

  38. Electric Motor • Current supplied creates and electric field around the coils are moved by the magnetic field. The motion makes the motor turn • Direct Current makes sure the motor only turns in one direction

  39. An electric generator produces an electrical current • by rotation loops of wire through a fixed magnetic field

  40. Armature • A coil of wire that is rotated in a magnetic field • More turns of coil the higher the voltage • Look at diagram of x-ray tube – • Armature surrounds neck of anode

  41. Used in x-ray equipment Magnets are turned on and off in sequence Electromagnets are used INDUCTION MOTOR

  42. There is only one wire – but works like when there are 2 wires = The windings are used as the primary and secondary coils The induced voltage varies on where the outside wires are connected (KVP Taps) Autotransformer – Self Induction

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