ElectromagnetismIn this chapter we will explore;

• The properties of magnetic fields and how they interact with one another. • Describe how electromagnetism is produced

from straight and coiled conductors.• Explain why a magnetic force is experienced

by a current carrying conductor immersed in a magnetic field; Predict the direction of the force produced.• Explain the operation of the DC motor.

12.1 Magnetic FieldsIn physics, a field is a region of space surrounding an object that can cause another object to experience a force. A magnetic field is a region of space surrounding a magnet that will exert a force on magnetic objects; alloys of iron, nickel, and cobalt.Earth has a magnetic field that exists both inside and surrounding it.Since the north-pole of a compass needle points north, it means the Earth’s geographic north pole must actually be a magnetic south-pole.

12.1 Magnetic Field LinesMagnetic fields exist in three dimensions surrounding a magnet and are more intense at the poles. They are invisible, but can be visually represented in diagrams with magnetic field lines.

Magnetic Field Lines:• Point from the north pole to the south pole outside of a magnet, and from

the south pole to the north pole inside of a magnet.• Never cross one another.• Are closer together where the magnetic field is stronger.

12.1 Magnetic Field LinesDrawing Field Lines:A compass can be used to map the direction of the field lines around a magnet.The compass needle will align itself along the direction of the field.

12.1 Magnetic Field LinesMagnetic fields cause an attraction between unlike poles (N-S), and a repulsion between like poles (N-N, S-S).

12.1 Magnetic Fields at WorkMaglev ‘magnetic levitation’ trains use magnetic fields for both levitation and forward motion. The train is able to float above the tracks, not making any contact with the tracks. This greatly reduced friction, allowing the train to travel at very high speeds.

Magnetic resonance imaging (MRI) machines use extremely strong magnetic fields to produce very detailed images inside the human body. These images help doctors diagnose diseases or provide information for surgery.

12.1 Magnetic Fields at WorkA particle accelerator is a machine that accelerates subatomic particles to near light speeds, making them collide with other particles. These collisions are analyzed to possibly find new particles. The Large Hadron Collider (LHC) is a particle accelerator in Switzerland that uses magnetic fields to control the path and speed of protons. Recently it was used to detect the Higgs boson, which is believed to be responsible for the mass of all particles.

12.1 Magnetic Fields in NatureThe aurora borealis, or the northern lights, display beautiful colours in the night sky near Earth’s North Pole. These are a result of Earth’s magnetic field interacting with charged particles from the Sun. The different colours result from collisions in the atmosphere with oxygen, hydrogen, nitrogen, and helium.

Even living creatures, such as birds and the spiny lobster, use Earth’s magnetic field to help navigate while migrating.

12.1 Homework

Questions # 1-6 p.552