SPH3U: Electricity Overview of Electromagnetism

Electricity & Magnetism Electricity and Magnetism are very closely related, since both are based on the properties of electrically charged particles. The Electromagnetic force is one of the four fundamental forces in nature (including the strong nuclear, the weak nuclear, and gravity).

Magnetic Fields and Current When an electric current moves through a wire, a magnetic field is produced. The magnetic field exists in circular rings around a straight conductor. The direction of the magnetic field depends on the direction of the current.

Magnetic Fields and Current Oersted’s principle: Whenever a charge moves through a straight conductor, a circular magnetic field is created around the conductor.

Magnetic Fields and Current The Right-hand Rule: when holding a straight conductor with your right hand and thumb pointing in the direction of conventional current, your curled fingers will point in the direction of the magnetic field lines.

Practice Draw the magnetic field lines around each wire. Current going into the pageCurrent going out of the page

Practice Draw the magnetic field lines around each wire.

The Motor Principal Since a current carrying wire has a magnetic field around it, an external magnetic field around the wire can cause the wire to move. This is because of the attraction or repulsion of the two magnetic fields (the one around the wire and the external one).

The Motor Principal This property is called the Motor Principal: A current-carrying conductor that cuts across external magnetic field lines experiences a force that is perpendicular to both the magnetic field and the direction of the electric current.

The Motor Principal The force is caused because the magnetic field lines on the magnet, and on the wire, are going in the same direction. Therefore there is a repulsion.

The Motor Principal Right-hand Rule for the Motor Principal: If the fingers of your open right hand point in the direction of the external magnetic field, and your thumb points in the direction of the conventional current, then your palm faces in the direction of the force on the conductor.

Practice Determine the direction of the force on the wire. X

Electromagnetic Induction Because of the relationship between electricity and magnetism, when a magnetic field changes near a conductor, an electric current can be produced.

Electromagnetic Induction This is how electricity is produced in a power-plant: When water (or steam) pushes the turbine, it will rotate a magnet. When the magnet is rotated, the magnetic field changes. When the magnetic field changes, a current is produced.

Videos Overview of the entire unit 8U5PhU 8U5PhU

Homework Read section 12.2 (pg ) and 12.5 (pg ). Supplement your notes by adding information from these sections. Do the following questions: Page 556 # 1-7 Page 566 # 1-2