Tham khảo tài liệu 'chapter 8: the steady magnetic fieldat', khoa học tự nhiên, vật lý phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | CHAPTER 8 THE STEADY MAGNETIC FIELD At this point the concept of a field should be a familiar one. Since we first accepted the experimental law of forces existing between two point charges and defined electric field intensity as the force per unit charge on a test charge in the presence of a second charge we have discussed numerous fields. These fields possess no real physical basis for physical measurements must always be in terms of the forces on the charges in the detection equipment. Those charges which are the source cause measurable forces to be exerted on other charges which we may think of as detector charges. The fact that we attribute a field to the source charges and then determine the effect of this field on the detector charges amounts merely to a division of the basic problem into two parts for convenience. We shall begin our study of the magnetic field with a definition of the magnetic field itself and show how it arsies from a current distribution. The effect of this field on other currents or the second half of the physical problem will be discussed in the following chapter. As we did with the electric field we shall confine our initial discussion to free-space conditions and the effect of material media will also be saved for discussion in the following chapter. The relation of the steady magnetic field to its source is more complicated than is the relation of the electrostatic field to its source. We shall find it necessary to accept several laws temporarily on faith alone relegating their proof to 224 I e-Text Main Menu Textbook Table of Contents THE STEADY MAGNETIC FIELD 225 the rather difficult final section in this chapter. This section may well be omitted when studying magnetic fields for the first time. It is included to make acceptance of the laws a little easier the proof of the laws does exist and is available for the disbelievers or the more advanced student. BIOT-SAVART LAW The source of the steady magnetic field may be a permanent
