Transcript Electricity and Magnetism

Electricity
and Magnetism
Notes 6
Let’s Review
• What makes up an atom?
• Electron, Proton, Neutron
• What charge does each have?
• Electron –
• Proton +
• Neutron Neutral
Let’s review some more!
• There are three ways you can
conduct a charge. Name the one that
involves conducting a charge through
rubbing?
• Friction
• Which one deals with being near the
charged object?
• Induction
Again, Lets review!
• Like charges ____________?
• Repel
• Unlike charges ____________?
• Attract
Still reviewing!
• What is voltage?
• The push of electrons.
• What is current?
• The flow of electrons.
• What is resistance?
• Holds back the current
Reviewing…
• What type of circuit is shown below?
…Reviewing…
• What type of circuit is shown below?
Yes!
• Now you will start writing the notes.
• Look at your paper for AC and DC
currents.
• Let us begin.
Direct Current
• Direct current flows in one
direction.
• Can be produced using a solar cell
or a chemical cell. A battery is a
combination of chemical cells.
DC Current
• Electrons are repelled by the
negative terminal of a battery
and attracted to the positive
terminal of a battery.
• When a circuit is connected to the
terminals the electrons will move
from the negative terminal to the
positive terminal.
Alternating Current
• AC current or alternating current
moves back and forth.
• Can be produced by a generator
using the principle of
electromagnetic induction.
• The current is produced when a
magnet moves relative to a coil of
wire.
AC Current
• Electrons are repelled by the
negative terminal and attracted to
the positive terminal
• Since the terminals are continually
changing from positive to
negative the current continually
changes direction.
Magnetism
1. force of attraction or repulsion
between unlike or like poles
2. due to the arrangement of electrons
3. closely related to electricity
Magnetic Poles
• like poles repel
Magnetic Poles
• unlike poles attract
Magnetic Poles
• a broken magnet creates new poles
Magnetic Field
1. area around a magnet where
magnetic forces act
2. field lines show direction of field
(NS)
Magnetic Domain
1. groups of atoms
with aligned
magnetic poles
Domain
2. in a magnetized
object, domains
are all aligned
Electromagnets
• Electric Currents in wires produce
magnetic fields around the wire.
• The magnetic field can be
strengthened in several ways.
A speaker uses
electromagnets
Electromagnet
Electromagnets
1. Wrapping the wire in a coil. The
greater the number of turns in
the coil, the greater the
increase in strength.
2. Adding a core. Iron vs. Al???
3. Increasing the current in the
coil will strengthen the
electromagnet.
Electric Motor
Motors
• Electric motors change electrical
energy to mechanical energy.
• Motors contain an electromagnet
called an armature.
• When an electric current runs
through the wire in the armature it
becomes magnetized.
Motors
• The armature spins because other
magnets in the motor push and pull
the armature and cause it to spin.
• Motors use the magnetic force from
magnets to spin an armature
(magnetized by an electric current)
• Where do we see motors?
Generators
• A generator changes mechanical
energy into electrical energy.
• Generators use electromagnetic
induction to produce an electric
current.
Generators
• When a wire or a coil of wire moves
relative to a magnetic field and
electric current can be produced.
This process is called
electromagnetic induction.
Generators
• In a generator at a power plant
some other type of energy such as
the energy in stream is used to turn
a turbine which spins a magnet in a
generator.
• The magnet spins past a coil of
wire. This moving magnetic field
pushes electrons through the
wire.
Generators
• A generator is similar to an electric
motor. A generator is an electric
motor working in reverse.
• Generators produce AC current.