Right hand law

Right hand rule or law . It is a method of determining vector directions , and is based on Cartesian planes . It is practically used in two ways; the first is mainly for linear vector movements and directions, and the second is for rotational movements and directions.


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  • 1 Laws
    • 1 First law of the right hand
    • 2 Second law of the right hand
  • 2 Applications
  • 3 See also
  • 4 References
  • 5 Sources


First law of the right hand

If a conductor cable is in a magnetic field , a force is exerted on the cable of a magnitude given by the following formula: F = iBLsenα Where: i = current flowing through the cable B = magnetic field L = cable length α = angle between the direction of the current and the direction of the magnetic field, as shown in figure 1.

If a current (i) flows through the cable in the direction shown by the thumb in the figure and the magnetic field (B) has the direction shown by the index finger, a current will be applied to the cable (i) force (F) that has the direction shown by the middle finger. In the case that there are N cables in the presence of a magnetic field, the induced magnetic force will be the force in a cable multiplied by N. Therefore the formula will be: F = NiBLsenα

Second law of the right hand

When an alternating current or direct current travels through a conductor (cable), it generates an invisible effect called electromagnetic field around it . This field forms circles around the cable as shown in figure 2. There are circles near and far from the cable simultaneously.

The magnetic field is more intense the closer it is to the cable and this intensity decreases as you move away from it, until its effect is null.

The direction of the magnetic flux can be found by knowing the direction of the current in the wire and using the Second Right Hand Law.

In the image you can see how the sense of the magnetic field is obtained with the help of the second law of the right hand. This effect is very easy to visualize in direct current .

The formula to obtain the magnetic field in a long conductor is: B = mI / (2 pd) Where:

– B: magnetic field –

– m: is the air permeability –

– I: current through the cable – p: Pi = 3.1416

– d: distance from the cable.

If there were N cables together the resulting magnetic field would be:

B = N m I / (2 pd)

The magnetic field in the center of a coil of N circular turns is:

B = N m I / (2R)

Where: R is the radius of the turn

Note: it is important to mention that:

– A current in a conductor generates a magnetic field.

– A magnetic field generates a current in a conductor.

However, the most popular applications use alternating current. For example:

– The reels; where energy is stored as a magnetic field.

– The transformers; where the alternating current generates an alternating magnetic field in the primary winding, which induces in the secondary winding another magnetic field that in turn causes a current, which is the transformer’s output alternating current.


The right-hand rule, apart from presenting a constant protocol, also offers a practical harmonic instrument applicable in many areas, including manufacturing.

Many machines and industrial processes observe this order for axes, vectors and axial movements , includes Robotics , in its 12 fundamental movements this rule applies.


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