Magnets and Magnetic Fields

Contents / notes

• Natural and artificial magnets.
• Magnetic properties of soft iron and steel.
• Methods of making magnets and demagnetisation.
• Concept of a magnetic field.
• Magnetic field of a permanent magnet.
• Magnetic field around a straight current-carrying conductor, circular wire and solenoid.
• Properties of the Earth's magnetic field: north and south poles, magnetic meridian, angle of dip and declination.
• Magnetic flux and flux density.
• Variation of magnetic field intensity over the Earth's surface.
• Applications of the Earth's magnetic field in navigation and mineral exploration.

Candidate objectives

• Give examples of natural and artificial magnets.
• Differentiate between the magnetic properties of soft iron and steel.
• Identify methods of making and demagnetising magnets.
• Describe how to prevent a magnet from losing its magnetism.
• Determine the flux pattern of an isolated magnet.
• Determine the flux pattern when two magnets are placed together pole to pole.
• Determine the flux of a current-carrying conductor, circular wire and solenoid, including solenoid polarity.
• Determine the flux pattern of a magnet placed in the Earth's magnetic field.
• Identify the magnetic elements of the Earth's field.
• Determine variations in the Earth's magnetic field over its surface.
• Examine applications of the Earth's magnetic field.