5 Electric and Magnetic Phenomena

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18 Οκτ 2013 (πριν από 4 χρόνια και 26 μέρες)

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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