Download PHYSICAL SCIENCE CHAPTER 7 (Magnetism and its uses) NOTES

PHYSICAL SCIENCE CHAPTER 7 (Magnetism and its uses)
NOTES
SECTION 1 (Magnetism)
1) Magnetism—refers to the properties and interactions of magnets.
a) Magnetic flux--refers to the invisible lines of force between two magnets.
Always flows from the North Pole to the South Pole. Like poles repel while
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N
S
S
unlike poles attract.
b) Magnetic field—refers to the area that contains the magnetic flux. Also known as the beta field.
i) The more flux lines you have in a specific area the stronger the magnetic field is.
ii) Magnetic flux lines never cross each other.
c) Magnetic poles—are where the magnetic force exerted by the magnet is strongest.
d) Magnetic domains—are the groups of atoms with aligned magnetic poles.
e) Temporary Magnets--have the ability to become magnetized but also may lose the magnetic capabilities easily.
f) Permanent Magnet--Are usually made of iron, aluminum, nickel, and cobalt. These materials keep their magnetic
capabilities.
2) Geographic North Pole--is a point on the earth that the imaginary line of the earth's axis passes through. If this line were
extended into space it would also pass through Polaris (the north star)
3) Magnetic North Pole--a point in northern Canada that is located about 2000 kilometers away from the geographic North Pole.
SECTION 2 (Electricity and Magnetism)
1) Electromagnetic Force—is the attractive or repulsive force between electric charges and magnets.
2) Electromagnetism—is the interaction between electric charges and magnets.
3) Electromagnet—is a temporary magnet made by placing a piece of iron inside a current-carrying coil of wire.
a) Left Hand Rule--(CONDUCTOR-- Engineers Point of View)--grasp the conductor in the left hand with
the fingers encircling the conductor the thumb point in the direction of the current. The fingers will point
in
the direction of the magnetic field.
b) Left Hand Rule--(SOLENOID--Engineers Point of View)--grasp the coil in the left hand with the fingers circling the coil
in the direction of the electron current. The extended thumb will point in the direction of the North Pole.
c) Solenoid--A wire spiral through which a current can flow. A magnetic field is created in side the coils when current is
flowing through the wire.
i) Two ways to increase the magnetic field. One is to increase the number of coils in the winding or increase the current
running through the wire.
ii) Permeability--is the property of a material by which it changes the flux density in a magnetic field from the value in air.
4) Galvanometer—which are devices that use and electromagnet to measure electric current.
5) Electric Motor--is a device that converts electric energy into mechanical energy. Uses alternating current and converts it into
rotary motion.
N pole
N pole
N pole
S pole
S pole
S pole
SECTION 3 (Producing Electric Current)
1) Electromagnetic Induction—producing an electric current by moving a loop
of wire through a magnetic field or moving a magnet through a wire loop.
2) Generators—produces electric current by rotating a coil of wire in a magnetic
field. Generators use electromagnetic induction to produce electricity.
a)
A
C
B
A simple generator consists of a loop of wire of a coil of several loops place in a magnetic field. As the coil rotates, it cuts
through the magnetic lines of force. This results in a current flowing through the wire.
i) Conductor moves parallel to the lines of flux no induce
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S pole
current.
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ii) Conductor cuts parallel lines of flux at angle some
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induced current.
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iii) Conductor cuts parallel lines of flux at maximum
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1
perpendicular angle induces maximum current.
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When a conductor is rotated through a magnetic field, the moving
conductor continuously cuts the parallel line of flux at varying
angles. This causes an induced current that continuously changes
directions. This is known as alternating current and if a graph of the
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N pole
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PHYSICAL SCIENCE CHAPTER 7 (Magnetism and its uses)
NOTES
induced current is produce a sine wave is generated.
3) Turbine—a large wheel that rotates when pushed by water, wind, or steam.
4) Direct current (DC)—electric current that only flows in one direction through the wire.
5) Alternating current (AC)—reverses the direction of the current flow in a regular way.
6) Transformer--is a device that uses electromagnetic induction to change the electric potential (voltage) of alternating current.
a) A transformer has a primary coil and a secondary coil. The alternating current in the primary causes a rising and falling
magnetic field that reverses direction with the alternating current. This reversing magnetic field in turn induces alternating
current into the secondary coil.
i) Step-Down Transformer--The secondary coil has fewer turns than the primary. V2 is dropped while I2 is increased.
ii) Step-Up Transformer--The secondary coil has more turns than the primary. V2 is increased while I2 is decreased.
A
B
7) Analog Signal--is a signal that is continuously changing. An analog signal will carry noise.
8) Digital Signal--is a series of electric pulses that stand for two digits, 0 and 1. Where the zero represents the switch is off and 1
represents the switch is on.
a) Bit--is a single digit in a series
b) Byte--is eight bits in a series is also known as a binary word.
c) A is an example of a analog signal B is a example of an analog signal being converted to a digital signal.
d) Digital Signals use logic in their circuits to perform certain tasks.
e) Inverter--inverts the input. Example if 1 is put into the circuit a 0 comes out.
f) AND, NAND, OR, NOR GATES--we will study these gates.
Inverter
Chapter 7 Equations
AND Gate
NAND Gate
Transformer Power Equation ⇒ PPRIMARY = PSECONDARY
Since P=I V then
OR Gate
NOR Gate
I1V1 = I 2V2
Transformer Equation ⇒
V1 V2
=
N1 N 2