Evans SPH 3U1

Physics Grade 11

Unit 5: Electricity & Magnetism

Note 10: Electromagnets and Applications

Reference: Chapter 17.2, 17.3

Electricity and magnetism are phenomena that are closely related.

Oersted's Principle: Charge moving through a conductor produces a circular magnetic field around the conductor.

Right Hand Rule #1 for Straight Conductors (for conventional current flow - NOT electron flow):

Grasp the conductor with the thumb of the right hand pointing in the direction of conventional (positive) current flow. The curved fingers point in the direction of the magnetic field around the conductor.

Right Hand Rule #2 for Coiled Conductors (for conventional current flow - NOT electron flow):

Grasp the coiled conductor with the right hand such that the curved fingers point in the direction of conventional current flow. The thumb points in the direction of the magnetic field within the coil. Outside the coil, the thumb represents the north end of the electromagnet produced by the coil.

Electromagnets (Qualitatively):

An electromagnet is a temporary magnet that operates when current flows through a coil of wire.

To strengthen an electromagnet, an iron core is placed inside the coil to concentrate the magnetic field.

Factors that determine an electromagnet's strength:

1) current in the coil

2) number of turns in the coil

3) type of material in the core of the coil

4) size of the coil (smaller diameter, stronger magnetic field)

5) magnetic permeability.

Applications of Electromagnetism:

Demonstrate the operation of a doorbell.

Complete student worksheets 13.4 (5 sheets) from Nelson.