Projekt Elektronik
Mess- und Regelungstechnik GmbH
Am Borsigturm 54 • 13507 Berlin
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Application Note PE004
Magnetic Field Basics
Magnetic Field Lines ............................................................................................................................................. 1
Right Hand Grip Rule ............................................................................................................................................ 1
Magnetic Field Lines
Magnetic field lines are always closed. Contrary to electrical
lines of flux they have neither a beginning nor an end. By
convention, magnetic field lines leave magnets or currentcarrying coils at the north pole, they reenter at the south pole
and they turn back within from S to N.
The field of a coil corresponds to that of a bar magnet.
There are no magnetic monopoles, only magnetic dipoles.
Fig. 1: Magnetic field lines
Right Hand Grip Rule
Magnetic force lines encircle a current in the sense in which you
need a corkscrew turn, so that it progresses in the direction of
positive current. Around a straight, current-carrying conductor, they
form concentric circles, lying in planes, that are perpendicular to
the conductor. The direction of the magnetic field is given by the
“Right hand grip rule”!
If one embraces the current-carrying conductor with the right hand
such that the thumb points in the (positive) current direction, then
the other fingers indicate the positive direction of the magnetic
field.
Fig. 2: Field lines of a current-carrying conductor
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