Home  Resources  References  Tubes  Forums  Links  Support  Sale  Search 



(See Fig. 10(b).) If the coil with current in it were suspended and allowed freedom of movement, it would turn and stand with its axes in an N and S line as a magnet needle would do; if we explore the lines of force with a magnet needle, we find they run through the coil S to N as well as outside N to S.


Fig. 9--Right hand rule for direction of current flow
     If a rod of steel is inserted into the coil and current is passed through it, the steel will become a permanent magnet. If instead of the steel we insert a rod of iron into the coil it also becomes a magnet, but it is only magnetic so long as the current lasts. This is called an electromagnet.
     A knowledge of magnets and magnetism is of the utmost importance in getting a thorough understanding of Radio, In

(a)--The sketch above illustrates the magnetic field surrounding a coil of wire carrying current.	(b)--Lines of force about a coil of wire carrying current.
Fig. 10

our study of Radio we shall often study the effects of lines of: force of various magnetic fields, we shall see later how lines of force cutting a wire can produce a voltage in another wire and how energy can be transferred from one part of a radio receiver to another, by these magnetic lines of force, even though there is not actual contact between the parts. Then we shall see also how the same principle is applied so that energy is transferred between a transmitting and receiving aerial.

11

Content	©1931, National Radio Institute
Webpage	©1997, Nostalgia Air
Transcriber	Richard Lancaster