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```					    Electricity and Magnetism at Work
Electricity , Magnetism, and Motion

Energy             Energy is the ability to move an object
some distance.

The energy associated with electric
currents is called electrical energy.

The energy an object has due to movement
or position is called mechanical energy.

When a current-carrying wire is placed in
a magnetic field, electrical energy is
converted into mechanical energy.

1
Electricity and Magnetism at Work
Electricity , Magnetism, and Motion

Galvanometer       A galvanometer is a device that uses the
rotation of a loop of wire in a magnetic
field to measure small amounts of current.

Electric Motor     An electric motor is a device that uses an
electric current to turn an axle. It converts
electrical energy into mechanical energy.

It is different from a galvanometer because
in a motor, a loop of current-carrying wire
spins continuously.

2
Electricity and Magnetism at Work
Electricity , Magnetism, and Motion

How a Motor         The direction of the force on the wire
Works               depends on the current and the magnetic
field surrounding the coil.

In a motor, current is reversed just as the
loop gets to the vertical position.

This reverses the force on each side of
the loop. The current reverses after each
half turn so that the loop spins
continuously in the same direction.

3
Electricity and Magnetism at Work
Electricity , Magnetism, and Motion

Commutator            A commutator is a device that reverses
the flow of current through an electric
motor.

Brushes              When the loop of wire rotates, the
commutator slides past two contact
points called brushes.

4
Electricity and Magnetism at Work
Electricity , Magnetism, and Motion

Armature             An armature is the moving part of an
electric motor, consisting of dozens or
hundreds of loops of wire wrapped
around an iron core.

Using many loops increases the strength
of the motor and allows it to rotate more
smoothly.

5
Electricity and Magnetism at Work
Generating Electric Current

Electromagnetic      If a wire is moved up and down between
Induction            a magnetic field, an electric current is
produced.

An electric current will be produced in a
conductor when the conductor moves
across the lines of a magnetic field.

Electromagnetic induction is the process
of generating an electric current from the
motion of a conductor through a magnetic
field.
6
Electricity and Magnetism at Work
Generating Electric Current

Induced Current          The flow of an induced current may be
constant, or may change direction.

Alternating Current      A current consisting of charges that move
back and forth in a circuit is an alternating
current. (ie. house)

Direct Current          A current consisting of charges that flow
in one direction only is called a direct
current. (ie. car battery)

7
Electricity and Magnetism at Work
Generating Electric Current

Electric Generator    An electric generator converts mechanical
energy into electrical energy.

An electric motor uses an electric current
to produce motion. A generator uses
motion to produce an electric current.

8
Electricity and Magnetism at Work
Generating Electric Current

Turbine            A turbine is a circular device made up

Mechanical energy turns the huge
turbines in electricity-generating plants.

Flowing water from a dam, wind, steam,
from the burning of fuels, and even the
ocean’s tides can be used to turn turbines.

9
Electricity and Magnetism at Work
Generating Electric Current

Solar energy           Solar energy makes use of the sun’s rays.

Wind energy            Wind energy is free, clean, has no waste,
and has an unlimited supply.

Geothermal energy     Geothermal energy uses steam from the
Earth’s interior.

10
Electricity and Magnetism at Work
Using Electric Power

Power             Power is the rate at which energy is
converted from one form to another.
The unit of power is the watt.

You can calculate power by multiplying
voltage by current.

Power = Voltage x Current
or
Watts = Volts x Amps

11
Electricity and Magnetism at Work
Using Electric Power

Paying for Energy     The electric bill that comes to your home
charges for energy use, not power.

The total amount of energy used by an
appliance is the power consumption
multiplied by the time the appliance is
in use.

Energy = Power x Time

12
Electricity and Magnetism at Work
Using Electric Power

Transformers      The most efficient way of transmitting
current over long distances is to maintain
very high voltages.
Voltage must be reduced before it can be

A device that increases or decreases
voltage is called a transformer.

13
Electricity and Magnetism at Work
Using Electric Power

Changing Voltage      A transformer that increases voltage is
called a step-up transformer.

A transformer that decreases voltage is
called a step-down transformer.

14
Electricity and Magnetism at Work
Using Electric Power

Alternating     Nikola Tesla invented alternating current,
Current         which replaced direct current.

Using alternating current with transformers
reduces energy losses in the long
transmission wires.

15
Electricity and Magnetism at Work
Batteries

Electrochemical   An electrochemical cell is a device that
Cell              converts chemical energy into electrical
energy.

An electrochemical cell consists of two
different metals called electrodes. The
electrodes are partially immersed in a
substance called an electrolyte.

16
Electricity and Magnetism at Work
Batteries

Electrolyte      An electrolyte is a substance that conducts
electric current.

Terminal        The part of an electrode above the surface
of the electrolyte is called a terminal. The
terminals are used to connect the cell to a
circuit.

17
Electricity and Magnetism at Work
Batteries

A Simple Cell    Chemical reactions occur between the
electrolyte and the electrodes in an
electrochemical cell. These reactions
cause one electrode to become negatively
charged and the other electrode to become
positively charged.

18
Electricity and Magnetism at Work
Batteries

Battery             A battery is a combination of two or more
electrochemical cells in a series.

The positive terminal of one cell is
connected to the negative terminal of the
next. The voltage of the battery is the sum
of the voltages of the cells.

19
Electricity and Magnetism at Work
Batteries

Wet Cell         An electrochemical cell in which the
electrolyte is a liquid is a wet cell.

Dry Cell         A dry cell is an electrochemical cell in
which the electrolyte is not really dry,
but a paste.

20

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