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Use the scrollbars to change the radius of the coil, the number of turns and the spacing between turns. As the cursor is moved over the field plot, the x,y coordinates and the strength of the field (in arbitrary units) are shown in the panel. Hold down the left mouse button to display a plotting compass.
![]() The screen above a 2D section through circular coil or solenoid. The blue circles indicate the current flowing out of the plane of the screen. The red circles indicate the current flowing into the plane of the scree.
A magnetic field is a region where a magnetic force is exerted on a moving electric
charge. For electric and gravitational fields, we can define field strength as the force
per unit charge or force per unit mass, however in the case of magnetic fields there is no
parallel definition, since there is nothing that corresponds to a unit charge or mass.
Consequently magnetic fields are defined in terms of the force, F acting on a charge,
Q moving at a speed v.
The magnetic field strength (flux density) B is then
![]() Magnetic fields are vector fields. i.e. each point in the field has a magnitude and a direction. The Field lines show
B is measured in units called Tesla |