Righthand rule
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In mathematics and physics, the righthand rule is a common mnemonic for understanding orientation of axes in 3dimensional space.
Most of the various left and righthand rules arise from the fact that the three axes of threedimensional space have two possible orientations. This can be seen by holding your hands outward and together, palms up, with the fingers curled. If the curl of your fingers represents a movement from the first or xaxis to the second or yaxis, then the third or zaxis can point along either thumb. Left and righthand rules arise when dealing with coordinate axes, rotation, spirals, electromagnetic fields, mirror images, and enantiomers in mathematics and chemistry.
Contents
Coordinates
Axis or vector  Two fingers and thumb  Curled fingers 

X, 1, or A  First or index  Fingers extended 
Y, 2, or B  Second finger or palm  Fingers curled 90° 
Z, 3, or C  Thumb  Thumb 
Coordinates are usually righthanded.
For righthanded coordinates your right thumb points along the Z axis in the positive direction and the curl of your fingers represents a motion from the first or X axis to the second or Y axis. When viewed from the top or Z axis the system is counterclockwise.
For lefthanded coordinates your left thumb points along the Z axis in the positive direction and the curled fingers of your left hand represent a motion from the first or X axis to the second or Y axis. When viewed from the top or Z axis the system is clockwise.
Interchanging the labels of any two axes reverses the handedness. Reversing the direction of one axis (or of all three axes) also reverses the handedness. (If the axes do not have a positive or negative direction then handedness has no meaning.) Reversing two axes amounts to a 180° rotation around the remaining axis.^{[1]}
Rotations
A rotating body
In mathematics a rotating body is commonly represented by a vector along the axis of rotation. The length of the vector gives the speed of rotation and the direction of the axis gives the direction of rotation according to the righthand rule: right fingers curled in the direction of rotation and the right thumb pointing in the positive direction of the axis. This allows some easy calculations using the vector cross product. Note that no part of the body is moving in the direction of the axis arrow, which takes some getting used to. By coincidence, if your thumb points north the earth rotates according to the righthand rule. This causes the sun and stars to appear to revolve according to the lefthand rule.
Helices and screws
A helix is a curved line formed by a point rotating around a center while the center moves up or down the Zaxis. Helices are either right or lefthanded, curled fingers giving the direction of rotation and thumb giving the direction of advance along the Zaxis.
The threads of a screw are a helix and therefore screws can be right or lefthanded. The rule is this: if a screw is righthanded (most screws are) point your right thumb in the direction you want the screw to go and turn the screw in the direction of your curled right fingers.
Electromagnetics
 When electricity flows in a long straight wire it creates a circular or cylindrical magnetic field around the wire according to the righthand rule. The conventional current, which is the opposite of the actual flow of electrons, is a flow of positive charges along the positive Zaxis. The conventional direction of a magnetic line is given by a compass needle.
 Electromagnet: The magnetic field around a wire is quite weak. If you coil the wire into a righthanded (or lefthanded) helix all the field lines inside the helix point in the same direction and each successive coil reinforces the others. The advance of the helix, the noncircular part of the current and the field lines all point in the positive Z direction. Since there is no magnetic monopole the field lines exit the +Z end, loop around outside the helix, and reenter at the −Z end. The +Z end where the lines exit is defined as the north pole. If you curl the fingers of your right hand in the direction of the circular component of the current your right thumb points to the north pole.
 Lorentz force: If a positive electric charge moves across a magnetic field it experiences a force according to the righthand rule. If the curl of your right fingers represents a rotation from the direction the charge is moving to the direction of the magnetic field then the force is in the direction of your right thumb. Because the charge is moving, the force causes the particle path to bend. The bending force is computed by the vector cross product. This means that the bending force increases with the velocity of the particle and the strength of the magnetic field. The force is maximum when the particle direction and magnetic fields are at right angles, is less at any other angle and is zero when the particle moves parallel to the field.
Ampère's righthand grip rule
Ampère's righthand grip rule^{[2]} (also called righthand screw rule, coffeemug rule or the corkscrewrule) is used either when a vector (such as the Euler vector) must be defined to represent the rotation of a body, a magnetic field, or a fluid, or vice versa, when it is necessary to define a rotation vector to understand how rotation occurs. It reveals a connection between the current and the magnetic field lines in the magnetic field that the current created.
AndréMarie Ampère, a French physicist and mathematician, for whom the rule was named, was inspired by Hans Christian Ørsted, another physicist who experimented with magnet needles. Ørsted observed that the needles swirled when in the proximity of an electric currentcarrying wire, and concluded that electricity could create magnetic fields.
Application
This version of the rule is used in two complementary applications of Ampère's circuital law:
 An electric current passes through a solenoid, resulting in a magnetic field. When wrapping the right hand around the solenoid with the fingers in the direction of the conventional current, the thumb points in the direction of the magnetic north pole.
 An electric current passes through a straight wire. Grabbing the wire points the thumb in the direction of the conventional current (from positive to negative), while the fingers point in the direction of the magnetic flux lines. The direction of the magnetic field (counterclockwise instead of clockwise when viewed from the tip of the thumb) is a result of this convention and not an underlying physical phenomenon. The thumb points direction of current and fingers point direction of magnetic lines of force.
The rule is also used to determine the direction .
Cross products
The cross product of two vectors is often taken in physics and engineering. For example, in statics and dynamics, torque is the cross product of lever length and force, while angular momentum is the cross product of linear momentum and distance. In electricity and magnetism, the force exerted on a moving charged particle when moving in a magnetic field B is given by:
The direction of the cross product may be found by application of the right hand rule as follows:
 The index finger points in the direction of the velocity vector v.
 The middle finger points in the direction of the magnetic field vector B.
 The thumb points in the direction of the cross product F.
For example, for a positively charged particle moving to the North, in a region where the magnetic field points West, the resultant force points up.^{[1]}
Applications
The right hand rule is in widespread use in physics. A list of physical quantities whose directions are related by the righthand rule is given below. (Some of these are related only indirectly to cross products, and use the second form.)
 For a rotating object, if the righthand fingers follow the curve of a point on the object, then the thumb points along the axis of rotation in the direction of the angular velocity vector.
 A torque, the force that causes it, and the position of the point of application of the force.
 A magnetic field, the position of the point where it is determined, and the electric current (or change in electric flux) that causes it.
 A magnetic field in a coil of wire and the electric current in the wire.
 The force of a magnetic field on a charged particle, the magnetic field itself, and the velocity of the object.
 The vorticity at any point in the field of flow of a fluid.
 The induced current from motion in a magnetic field (known as Fleming's righthand rule).
 The x, y and z unit vectors in a Cartesian coordinate system can be chosen to follow the righthand rule. Righthanded coordinate systems are often used in rigid body and kinematics.
See also
Wikimedia Commons has media related to Righthand rule. 
 Chirality (mathematics)
 Curl (mathematics)
 Fleming's lefthand rule for motors
 Improper rotation
 ISO 2
 Oersted's law
 Pseudovector
 Reflection (mathematics)
References
External links
 Right and Left Hand Rules  Interactive Java Tutorial National High Magnetic Field Laboratory
 A demonstration of the righthand rule at physics.syr.edu
 Weisstein, Eric W. "Righthand rule". MathWorld.
 Dr. Johannes Heidenhain : Right Hand Rule  Heidenhain TNC Training : heidenhain.de
 Christian Moser : righthandrule : wpftutorial.net