Field Directions

The direction of the field lines shows how a compass would line up if placed at that point. We can use the right hand grip rule to remember the relationship between current and field around a wire:

Grab the wire with your right fist (as shown), thumb pointing up: this is the direction of conventional current ( + to - ). Your curled up fingers show the direction of the field.

An alternative way of remembering this is called the corkscrew rule: when screwing in a corkscrew to a bottle of wine, the point indicates the direction of the current, the the turning the field direction.

N.B. This does not, of course, work with left-handed corkscrews!

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