Mr. Perez

1
Mr. Perez

• Grade 6 Science
• Electricity and Magnetism

2
Oersteds Discovery

• In 1820, Hans Christian Oersted connected a
  simple circuit made of a battery and wire
• He noticed that the needle in his compass moved
  every time the current flowed through the wire

• Why was this important?
• Oersted discovered that an electric current
  causes a magnetic field
• He discovered that magnetism can be created from
  electricity

3
Electromagnetism

• What is electromagnetism?
• The relationship between electricity and
  magnetism is called electromagnetism
• When an electric current flows through the coils
  of a wire, the wire acts like a magnet
• The direction of the magnetic field changes with
  the direction of the current (from a generator)

• The magnetic field lines form circles

4
Electromagnets

• An electromagnet is a temporary magnet made by
  wrapping a wire coil carrying a current around an
  iron core

• The magnetic field inside a loop of wire is
  stronger than the magnetic field in a straight
  wire

5
Solenoids

• A single wire wrapped into a cylindrical wire
  coil is called a solenoid
• If the solenoid is wrapped around an iron core
  (like a nail), an electromagnet is formed.
• The solenoids magnetic field with the iron core
  is more than 1,000 times greater than the
  solenoid alone

6
Properties of Electromagnets

• Electromagnets are temporary magnets because the
  magnetic field is only present when the current
  flows through them
• The strength of the magnetic field can be
  increased by adding more turns of wire OR
  increasing the current
• Electromagnets will align along magnetic field
  lines like a compass
• Electromagnets will attract magnetic materials
  and will be attracted or repelled by other magnets

7
Generating Electricity for Homes

• Electrical energy comes from a power plant with
  huge generators
• The coils in these generators have many coils of
  wire wrapped around huge iron cores.

• The rotating magnets are connected to a
  turbine, which is a large wheel that rotates when
  pushed by water, wind, or steam

8
Transmitting Electrical Energy

• When the electric energy is transmitted along
  power lines, some of the electrical energy is
  converted into heat due to the electrical
  resistance of the wires
• The electrical resistance and heat production
  increases as the wires get longer
• Transformers can be used to reduce this heat

Electromagnetic Induction is the process by which
an electric current is produced by moving a wire
in a magnetic field
9
Transmitting Electrical Energy

• One way to reduce the heat produced in a power
  line is to transmit the electrical energy at high
  voltages, typically around 150,000 V
• Step-up transformers are used to push high
  voltage along power lines
• Electrical energy at such high voltage cannot
  enter your home safely, nor can it be used in
  home appliances
• A step down transformer is used to decrease the
  voltage before it enters your home

10
Transformers

• A transformer is a device that increases or
  decreases the voltage of an alternating current
• It is made out of a primary coil AND a secondary
  coil
• The wire coils are wrapped around the same iron
  core, which creates the magnetic field in the
  iron core

The voltage in the primary coil is the input
voltage, and the voltage in the secondary coil is
the output voltage
11
Step-Up and Step-Down Transformers

• Step-Down Transformers decrease voltage (for use
  in homes)

• Step-Up Transformers increase voltage (for use in
  power lines)

12
Transmitting Alternating Current

• This figure shows how energy from power plants
  reaches your home
• Electric motors, such as an electric fan, changes
  electrical energy into mechanical energy(and are
  used in dvd players, hair dryers, computers, and
  other appliances)

13
Electromagnets and Sound

• The electromagnet changes electrical energy to
  mechanical energy that vibrates the speaker cone
  to produce sound.