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6. Intro to Electricity
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The Forces in Creation - Part 2
Text: Module 12 pages 285 - 310
Reading Assignments
Module 12 pp 285 - 287
Module 12 pp 288 - 310
Homework Assignment
Module 12 Study Guide Questions p 310 # 1-10
Module 12 Study Guide Questions p 311 # 1-20
Introduction (p 284)
• The electromagnetic force is a fundamental
force due to the movement interactions of
the charges associated with electrons.
• James Maxwell (p 284 -285)
– Discovered and proved that electricity and
magnetism were caused/governed by the same
force now called the electric force.
– also act as transmission media for sound. ALL
waves excerpt for one (electromagnetic waves)
requires a medium - something to move through.
Two General Type of Waves (p
353)
• Transverse - wave that propagates
perpendicular to its direction of
occultation.
• Longitudinal - waves that propagates
parallel to its direction of occultation.
– Compression - area of compression
(higher pressure/greater density) - like
crest
– Rarefaction - pulled apart lower
pressure/lower density - like trough.
Some Specific Types of Waves
Photon explanation of the inverse square law. (Page 291)
The Electromagnetic Force (p
286 - 287)
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Likes charges repel
Opposite charges attract
Rules of EM force (p 289)
All EM charges either attract or repel each other
Likes charges repel Opposite charges attract
• The force is directly proportional to the amount of
electrical charge on each object
• The force is inversely proportional to the square of
the distance between the two objects.
• F = Kq1q2/r2
Experiment 12.1: Electrical
Attraction and Repulsion (p 286)
• Photons and the Electromagnetic Force
• Electromagnetism has a due nature - it can act as wave and a
particle. We don't understand this because logically (deductive
logic) a particle can't be a wave and a wave can't be a particle. A
wave should be the movement of energy through some medium
(bunch of particles). But light violates this rule in that it sometimes
acts as a particle and sometimes act as wave.
• In this section we will look at Electromotive force in terms of
particle called photons.
• Photon - small packet of "light" that acts like a particle.
• Review the EM spectrum to reinforce that we only see a small part
of the EM spectrum.
• Radio - Microwaves
• Infra red
• Red - Yellow - Green - Violet
• Ultra violet
• X-rays, Gamma rays
How Objects become Electrically
charged. (P 291 - 295)
• Separation of Charges (p294 - 295)
• Charging by conduction - charging by
contact with another charged object
• Charging by induction - charging with
direct contact (inducing the charge)
Experiment 12.2 Making and
Using and Electroscope (p292)
Electrical Circuits (295)
• Electrical Circuit: a set of wires that can conduct
electricity - allow electrons to flow.
• Review atoms and molecules - concept of a metal
and a sea of electrons.
• Electrical Currents: The amount of charge that
passes a given point of a electrical circuit
• Conventional drawing of a current - why it is done
backwards from electron flow.
• Electrical Current terms
• Amperage - rate of flow of current (think of the
volume of water in a river)
• Voltage - the change in potential energy across two points of a
circuit (sometimes also called electric potential difference or
electrical tension). It can be thought of in terms of the rate of
change in the river elevation. You may have heard the
expression it is not the voltage but the amperage that kills you.
Think of a waterfall - if the water fall is very high (high voltage)
but has a trickle of water (low amperage it wont hurt you) (It is
the potential similarity of electrical potential between two
points of an electrical or electronic circuit, expressed in volts. It
measures the potential energy of an electric field to cause an
electric current in an electrical conductor. Depending on the
difference of electrical potential it is called extra low voltage,
low voltage, high voltage or extra high voltage.
• Resistance (p 300) - The ability of a
substance to impede electrical flow.
• Metal good conductors, poor resistors
• Plastic good resistor, poor conductor.
• Concept of heating element - little bit of
both.
Experiment 12.3 Current and
Resistance
Switches and Circuits (p 302)
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Open versus closed circuit
Series and Parallel Circuit
Series - one goes out all goes out
Parallel - one goes out other stay on.
Magnetism (p 305)
• Movement of charge particle produce a magnetic
force
• Instead of positive and negative charges, we have
north and south poles
• The north pole of a magnet attracts electrons. The
south magnetic pole repels electrons. (complicated
because electrons both move forward (translate) and
spin (rotate)
• Like poles repel and opposite poles attract.
• Terms of magnetism:
– Dipole (versus monople)
– Magnetic filed lines
– Magnetic filed of the earth.
Permanent Versus Induced
Magnets
• "permanent" magnet is one which stays magnetized
for a long time, such as magnets often used in
refrigerator doors. Permanent magnets occur
naturally in some rocks, particularly lodestone, but
are now more commonly manufactured.
• Induced Magnets are "soft" or "impermanent"
magnet is one which loses its memory of previous
magnetizations. "Soft" magnetic materials are often
used in electromagnets to enhance (often hundreds
or thousands of times) the magnetic field of a wire
that carries an electrical current and is wrapped
around the magnet; the field of the "soft" magnet
increases with the current.