Download 10.4 PPT Magnetism from Electricity

Electromagnetism
Utilizing electricity to create
and use magnetic fields
Electricity and Magnetism
• Relationship discovered in 1820 by Danish
scientist Hans Christian Oersted
• Electricity and Magnetism are different
parts of one force called the
electromagnetic force
• Moving electric charges create a magnetic
field
Solenoids & Electromagnets
• When a wire carrying
a current is looped,
the magnetic fields
combine to make the
wire act like a bar
magnet
• The field through the
center is very strong.
• Loop it more, it gets
stronger
Solenoids & Electromagnets
• A coil of current-carrying wire that causes
a magnetic field is called a solenoid
• Place a ferromagnetic (iron based)
material in the middle of the coil…you
have an electromagnet (This greatly
increases the strength of the magnetic
field produced by a solenoid)
Solenoids & Electromagnets
• Changing the current in the wire controls
the strength and direction of the magnetic
field produced
• The current can also be used to turn the
magnetic field on and off. Scientists
manipulate current and magnets when
making devices we use every day
Solenoids & Electromagnets
• The strength of an electromagnet depends
on:
– The current in the solenoid (more current 
more strength)
– The number of loops in the coil (more loops 
more strength)
– The type of material in the core
Electromagnetic Devices
• Electromagnets can take electrical energy
(from the moving electrons in current) and
change it into motion that can do work
• Electromagnetic devices thus change
electrical energy into mechanical energy
– Door bells
– Electric motors
– Loudspeakers
– Galvanometers
Galvanometers
• Measure small
amounts of current
using a solenoid
• Used in gas gauges
where a sensor in the
gas tank reduces
current as the tank
gets low
Electric Motors
• Use an electromagnet
to turn an axle
• When current flows,
one side of the
armature is pushed
and the other is pulled
• Current continues to
change direction,
which causes the axle
to spin
Electromagnets at Work!