Chapter 11

• larger the diameter of a wire, the more current it can carry
• The smaller the diameter of a wire, the less current it can carry.
• An insulator is any material that resists or prevents the flow of electric charge, such as electrons.
• The resistance of an insulator is very high
• An insulator provides the equivalent of an open circuit with practically infinite resistance and almost zero current
• AWG


  American Wire Gage
• B and S


  Brown and Sharpe Gage
• The gage numbers specify the size of round wire in terms of its diameter and cross-sectional area.
• As the gage numbers increase from 1 to 40, the diameter and circular area decreases
• high gage number indicate thinner wire size
• The circular area doubles for every three gage sizes
• The higher the gage number and the thinner the wire, the greater the resistance of the wire for any given length.
• hookup wire for electronic circuits with current of the order of milliamperes is generally about No. 22 gage. For this size, 0.5 to 1 A is the maximum current the wire can carry without excessive heating
• 1 mil = 0.001 in
• circular mil area = d^2 mils
• Most wire conductors are copper due to its low cost, although aluminum and silver are also used sometimes
• Tinned wire is easier to solder for connections
• Solid wire is made of only one conductor. If bent or fl exed repeatedly, solid wire may break.
• solid wire is used in places where bending and fl exing is not encountered.
• Stranded wire is made up of several individual strands put together in a braid
• Stranded wire is fl exible, easier to handle, and less likely to develop an open break.
• Very thin wire, such as No. 30, often has an insulating coating of enamel or shellac
• Very thin wire, such as No. 30, often has an insulating coating of enamel or shellac
• The braided conductor in Fig. 11–4c is used for very low resistance. It is wide for low R and thin for fl exibility, and the braiding provides many strands.
• Constant spacing between two conductors through the entire length provides a transmission line.
• Coaxial cable with an outside diameter of ¼ in. is generally used for the signals in cable television
• Coaxial cable, therefore, is a shielded type of transmission line
• In operation, the inner conductor has the desired signal voltage with respect to ground, and the metallic braid is connected to ground to shield the inner conductor against interference.
• With twin-lead wire, two conductors are embedded in plastic to provide constant spacing
• twin lead wire


  This type of line is commonly used in television for connecting the antenna to the receiver. In this application, the spacing is 5 ⁄8 in. between wires of No. 20 gage size, approximately. This line is not shielded.
• true


  The plastic coating on wire conductors has very high R
• true


  Coaxial cable is a shielded transmission line
• true


  With repeated bending and fl exing, solid wire is more likely to develop an open than stranded wire
• The spade lug


  is often used for screw-type terminals.
• The alligator clip


  is convenient for a temporary connection. Alligator clips come in small and large sizes
• The banana pins


  have spring-type sides that make a tight connection
• The terminal strip


  provides a block for multiple solder connections.
• The RCA-type plug


  is commonly used for shielded cables with audio equipment. The inner conductor of the shielded cable is connected to the center pin of the plug, and the cable braid is connected to the shield. Both connections must be soldered
• The phone plug


  still used in many applications but usually in a smaller size. The ring is insulated from the sleeve to provide for two connections. There may be a separate tip, ring, and sleeve for three connections. The sleeve is usually the ground side
• F connector


  It is universally used in cable television because of its convenience. The center conductor of the coaxial cable serves as the center pin of the plug, so that no soldering is needed. Also, the shield on the plug is press-fi t onto the braid of the cable underneath the plastic jacket