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There are a few forms of this rule, and it can be applied in many ways. Originally, it was a trick for right-handed coordinate systems to determine the direction of the magnetic field surrounding a long, straight wire carrying a current. Note that the magnetic field lines form circles around the wire.

This is how it works. Orient your right hand so that your thumb is along the direction of the current. The four fingers wrap in the direction of the magnetic field.

This has immediate application for determining the orientation of the z-axis basis unit vector, , in terms of the x- and y-axes' basis unit vectors; curl your right hand in the direction of to , and your thumb will point in the direction of cross . The rule is also applicable in several practical applications, such as determining which way to turn a screw, etc. There is also a left-hand rule, which exhibits opposite chirality.

Right-Hand Rule

 

The right hand rule applies to the flows of positive charges. If negative changes are flowing, simply use your left hand. The right hand rule can also be used to find the force induced by the presence of a magnetic field and the velocity of a particular particle. When a charge is placed in a magnetic field, that charge experiences force if:

  1. the charge is moving relative to the magnetic field,
  2. the charge's velocity has a component perpendicular to the direction of the magnetic field

The following video will explain these two applications of the right hand rule