CHAPTER 25 Magnetism and Electromagnetism

• State the laws of magnetic pole interactions.
• Recall the classes of magnetic materials as ferromagnetic, paramagnetic or diamagnetic.
• Describe the induction process for producing a permanent magnet from magnetic substances.
• List the characteristics of magnetic fields as well as the rules and conventions for the representation.
• Recognise the features of the earth's magnetosphere and it's biological significance.
• Recognise the significance of the discoveries of Oersted and Faraday in the development of electromagnetics.
• Calculate , using simple situations, the nature of magnetic fields surrounding wires, flat coils and solenoid coils.
• Describe the factors influencing the magnitude and direction of magnetic fields including simple vector combinations.
• Calculate the force acting between parallel conductors in a magnetic field.
• Define the nature of torque acting on a freely pivoted coil in a magnetic field.
• Describe the basic components and method of operation of simple DC motors as an application of the motor principle.
• List practical applications of electromagnetism and the motor principle in the home, industry, medical and research fields.

Scientific processes

• Sketch magnetic field patterns of single and multiple magnets, electromagnets or combinations of all three.
• Predict the behaviour of magnets or electromagnets when any given interaction is presented.
• Classify magnetic substances on the basis of their behaviour within any given field.
• Contribute to discussion and create presentations of practical magnetic and electromagnetic applications.
• Follow procedures to construct a working model of electrical meters and motors.
• Extrapolate basic theory principles to explain the operation of industrial, research and medical applications of electromagnetics.
• Quantify and organise data with correct units in magnetics and electromagnetics.
• Construct simple models which allow the explanation of electromagnetic effects.

Complex reasoning processes

• Solve complex problems using the formulae and techniques of magnetic fields and their applications.
• Integrate several pieces of basic magnetic or electromagnetic theory in order to predict the outcome of a complex interaction of fields.
• Research and demonstrate creative thinking in understanding new applications of electromagnetic principles.
• Debate the need for complex, expensive tools of the physicist for fundamental research.

CHAPTER 25 SUMMARY

• The region of influence where a magnet exerts a force is called a magnetic field.
• Magnetic substances are divided into ferromagnetic, paramagnetic and diamagnetic classes.
• Magnetism can be produced by a process of induction.
• The magnetic domain theory allows an explanation of both permanent and temporary magnetic effects.
• The Earth's magnetic field, or magnetosphere, has varied throughout geological history but provides a shield for all life on Earth.
• Directions of magnetic flux can be represented conventionally as lines traversing from north pole to south pole. Magnetic flux (Ø = B x A)
• Magnitudes of magnetic field strength vectors can be defined for basic electromagnet applications such as single current carrying wires, flat coils and solenoid coils, and are measured in units called tesla (T).
• Directions of electromagnetic forces and effects can be predicted using right hand rules.
• The motor principle states that the force acting on a current carrying conductor within a magnetic field is perpendicular to both the field and the direction of magnetic flux and is given by (F = B I L sin Ø).
• The motor principle is the basis for the operation of simple DC electric motors and explains rotational motion in terms of torque (t).
• Charged particles are influenced by magnetic fields in such a way that their path of travel is a curve of radius (r) by a force whose magnitude is (F = q v B)
• Many technological applications exist for basic magnets, electromagnets and their effects on charged particles.

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