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Applications 0f
Electricity
Electricity and Magnetism
Positive and Negative
Charge
Conductors and Insulators
Superconductivity
The Ampere
Potential Difference
Electric Power
Magnets
Magnetic Field
Electromagnets
Electromagnetic Induction
Transformers
Positive and Negative
Charge
Opposites attract-Same charges
repel
Positive and Negative Charge
Electrons are stripped
from one component
and transferred to the
other to cause both to
be oppositely charged.
Semiconductors
Transistors are switches that conduct
electricity only when a second source of
electricity is energized.
A
John Bardeen
Nobel Prizes in 1956
and 1972 for developing
the transistor and
superconductivity.
B
C
A current will not flow from A to B unless C is energized.
Superconductivity
Superconductivity
refers to the loss of all
electrical resistance by
certain materials at very
low temperatures.
Substances that are
superconducting at
150K are now known
which is warmer than
liquid nitrogen (77K).
The Ampere
The Ampere is a measure of how much electrical
current is flowing and is measured in units of amps.
The Ampere
The current varies depending on the force behind
the current and the resistance to flow.
Electric Power
The power of an electric current is the rate at which
it does work and is equal to the product of the
current and the voltage of a circuit:
The unit of electric power is the watt.The
commercial unit of electric energy is the
kilowatthour (kWh).
Electric Power
Typical Power Ratings
Appliance
Stove
Clothes Dryer
Heater
Dishwasher
Photocopier
Iron
Vacuum Cleaner
Coffee Maker
Refrigerator
Portable Sander
Fan
Personal Computer
TV Receiver
Fax Transmitter/Receiver
Charger for Electric Toothbrush
Power (W)
12,000
5,000
2,000
1,600
1,400
1,000
750
700
400
200
150
150
120
65
1
Magnets
A magnet is an object or a device
that gives off an external magnetic
field.
Every magnet has a north pole
and a south pole.
Magnet Field
Magnetic fields are areas where an
object exhibits a magnetic
influence. The fields affect
neighboring objects along things
called magnetic force lines.
Magnetic poles are the points
where the magnetic field lines
begin and end.
Magnetic force lines.
Electromagnets
An electromagnet consists of an iron core placed
inside a wire coil. The magnetic field strength of a
wire coil carrying an electric current increases in
direct proportion to the number of turns of the coil.
Electromagnets
An electromagnet can
be used to move large
quantities of metal.
When the current is on
the magnet will pick up
the metal. When you
want to drop it you turn
off the power and the
electromagnet is
disabled and the metal
drops.
Electric Motors
An electric motor uses
the sideways push of
a magnetic field to
turn a current-carrying
wire loop. Electric
motors use a
commutator to
change the direction
of the current in the
loop. Alternating
current electric motors
do not use
commutators.
Electromagnetic Induction
The effect of producing an
induced current is known as
electromagnetic induction.
The direction of the induced
current can be reversed by
reversing the motion of the wire
or reversing the field direction.
The strength of the current
depends on the strength of the
magnetic field and the speed of
the wire's motion.
Michael Faraday (17911867) built the first electric
motor and discovered
magnetic induction.
The stationary windings of a large electric
motor. magnetic forces underlie the operation
of such motors.
Sharks navigate with the help of the earth’s
magnetic field. They detect the field using
electromagnetic induction.
Transformers
A transformer is a device composed of two unconnected
coils, usually wrapped around a soft iron core, that can
increase or decrease the voltage of ac current.
A transformer is used to step the voltage
down and the power up (P=IV) so that we
can use it. Low power is desired for the
transport of electricity long distances to
avoid loss of energy to heat loss.
A moving coil
activated by voice
vibrations is used
as a microphone.
The coil induces a
current in the
magnet that can be
amplified or
recorded.
A taperecorder records signals from a microphone on
magnetic tape which then can be run across a magnet and
played back.
1. Who won the Nobel Prizes in 1956 and 1972 for developing the transistor and
superconductivity.?
2. It refers to the loss of all electrical resistance by certain materials at very low
temperatures.?
3. It is a measure of how much electrical current is flowing and is measured in
units of amps.?
4. These are areas where an object exhibits a magnetic influence.?
5. It is consists of an iron core placed inside a wire coil and also used to move
larges quantities of metal.?
6. What is the effect of producing an induced current.?
7. It is an object or a device that gives off an external magnetic field.?
8. What do you called the points where the magnetic field lines begin and end. ?
9. It is a device composed of two unconnected coils, usually wrapped around a
soft iron core, that can increase or decrease the voltage of ac current. ?
10. Use to change the direction of the current wire loop.?