# Right-Hand Grip Rule

A graphic illustrating the right-hand grip rule. A current carrying wire with its magnetic field and a hand indicating the right-hand grip rule are shown.

**Fleming's right**-**hand rule** (for generators) shows the direction of induced current when a conductor moves in a magnetic field. It can be used to determine the direction of current in a generator's windings.

This rule allows you to predict the direction of the circular magnetic field which is created around a conductor when current flows through the wire.

Point your right thumb in the direction of (conventional) current flow, and then curl your fingers around the wire. Your fingers now point in the same direction as the circular magnetic field around the conductor.

Ampère's right hand screw rule (also called *right-hand grip rule*, *coffee-mug rule* or the *corkscrew-rule*) 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.

André-Marie 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 current-carrying wire, and concluded that electricity could create magnetic fields.

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 of the torque vector. When gripping the imaginary axis of rotation of the rotational force so that your fingers point in the direction of the force, the extended thumb points in the direction of the torque vector.

**Applications:**

The right hand rule is in widespread use in physics. A list of physical quantities whose directions are related by the right-hand 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 right-hand 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 velocityvector.
- 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 right-hand rule).
- The x, y and z unit vectors in a Cartesian coordinate system can be chosen to follow the right-hand rule. Right-handed coordinate systems are often used in rigid body and kinematics.