4/18/2012
1
Electric and Magnetic
Phenomena
Electric and magnetic phenomena
are related and have many practical
applications.
5a
: Direct Current
•
Students know how to predict the voltage or
current in simple direct current (
DC) electric
circuits constructed from batteries, wires,
resistors, and capacitors
.
•
Battery: provides
electric potential
–
Symbol: _________or_________
•
Resistor: slows
current
, changes electrical energy
to
heat
and/or
light
–
Symbol: ______
•
Wires: carry current through a circuit
–
Symbol:
lines
5b: Ohm’s Law
•
Students know how to solve problems
involving Ohm's law.
•
V = I R
–
V:
voltage
–
I:
current
–
R:
resistance
5c: Power
•
Students know any resistive element in a DC
circuit dissipates energy, which
heats
the
resistor. Students can calculate the power (rate
of energy dissipation) in any resistive circuit
element by using the formula P =
VI
=
I
2
R
.
5d: Transistors
•
Students know the properties of transistors
and the role of transistors in electric circuits.
•
Transistors modify
current
–
Often as an
amplifier
•
Transistors are used in
any electronic device
5e: Charges
•
Students know charged particles are sources
of electric fields and are subject to the forces
of the electric fields from other charges.
•
Charges are
negative
(extra electrons) or
positive
(lack of electrons
•
Opposite charges
attract
•
Like charges
repel
4/18/2012
2
5f: Magnetism
•
Students know magnetic materials and electric
currents (moving electric charges) are sources of
magnetic fields
and are subject to forces arising
from the magnetic fields of other sources.
•
North
and
South
Poles
–
Opposites
attract
, likes
repel
•
Moving charges
induce
a magnetic field
•
Magnetic fields
induce a force
on moving charges
5g: Induced Magnetic Field
•
Students know how to determine the direction
of a magnetic field produced by a current
flowing in a straight wire or in a coil.
•
Right Hand Rule
–
Thumb:
straight current in a wire
or
magnetic field in
a coil
–
Curled fingers:
magnetic field around a wire
or
current in a coil
5h: Induced Current
•
Students know changing magnetic fields
produce electric fields, thereby inducing
currents
in nearby conductors.
•
Current can be created in a wire without
anything directly
connected
to it
5i: Plasma
•
Students know plasmas, the fourth state of
matter, contain ions or free electrons or both
and
conduct electricity
.
•
Plasma:
superheated gas
•
Lightning
is plasma of air
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