N1 Engineering Science|The Easy Way! 115 6.12.4 Screw rule


The direction of travel represents the direction of current flow and the direction of turning, the direction of the flux.


Current flows in


Current flows out Fig. 6.10 Screw rule 6.12.5 Magnetic field set up by current-carrying coil (solenoid)


Te magnetism associated with a current-carrying conductor can be intensified by forming the conductor into a coil or solenoid.


N ↑I Fig. 6.11 (a) Parallel conductors Fig. 6.11 (a) Parallel conductors I↓ Fig. 6.11 (b) Solenoid or coil g. 6.11 (b) Solenoid or coil


It may be seen how a field is established around a coil by first considering two parallel conductors, carrying current in the same direction as in fig. 6.11 (a). Lines of force pass around each conductor in the same direction, resulting in a field that entirely surrounds the two conductors.


The field set up by a coil or solenoid is shown in fig. 6.11 (b), where the lines of flux completely surround the conductors and are similar to those produced by a permanent magnet.


Te polarity of a magnetic field may be given by the Right-hand grip rule. 6.12.6 The right-hand grip rule


If the solenoid is gripped in the right hand with the fingers pointing in the direction of the current, the outstretched thumb then points to the north end of the solenoid, fig. 6.12.


S =


N


S


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