Electromagnets

1 / 9

# Electromagnets - PowerPoint PPT Presentation

Electromagnets. Oersted noticed that a compass needle moves whenever it is placed near a conducting wire. Oersted`s Principle : A charge moving through a conductor produces a circular magnetic field around the conductor.

I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.

## PowerPoint Slideshow about 'Electromagnets' - ziya

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript

Oersted noticed that a compass needle moves whenever it is placed near a conducting wire.

Oersted`s Principle: A charge moving through a conductor produces a circular magnetic field around the conductor.

• To determine the direction of the circular magnetic field (clockwise or counter clockwise) we use the Left Hand Rule (LHR) for straight conductors

Your thumb shows the direction of electron flow and your fingers wrap around the conductor in the direction of the magnetic field lines.

Don’t confuse LHR with RHR (in the book) that shows flowof positive charges.

• We use the designation of an X to show the flow of electrons going into the paper (face on), and the designation of a to show the flow of electrons coming out of the paper.
• Dashed lines in concentric circles represent the magnetic field lines which are closest together (strongest) nearest the conducting wire.
Solenoids

We can straighten out these magnetic field lines by “bending” the conductor into circles. This actually strengthens the magnetic field since the field lines become superimposed on one another. The advantage of this strategy is being able to create a strong magnet that can be turned on or off with current flow (electromagnet). This has many applications like stereo speakers, school bells, car remote devices.

To determine the direction of the magnetic field when current is travelling through a coiled conductor we use the Left Hand Rule (LHR) for coiled conductors.

Your thumb shows the direction of north magnetic fieldand your fingers wrap around the conductor in the direction of the electron flow.

Strength of Coiled Magnets

The magnetic field strength can be varied by:

• Current (more current increases magnetic field)
• Number of coils (more coils increases magnetic field)
• Size of coil (smaller diameter increases field strength)
• Type and amount of ferromagnetic conductor can increase magnetic field strength

Magnetic field strength is measured in units of Tesla (T)

• 1 Tesla equals 1 Newton of magnetic force when 1 Ampere of current travels through 1 metre of conductor
• Or 1 T = 1 N

mA