electromagnetism In physics, electromagnetism is an interaction that occurs between particles with electric charge. It is the second-strongest of the four fundamental interactions, after the strong force, and it is the dominant force in the interactions of a ...

, Fleming's right-hand rule (for generators) shows the direction of

induced current Electromagnetic or magnetic induction is the production of an electromotive force (emf) across an electrical conductor in a changing magnetic field. Michael Faraday is generally credited with the discovery of induction in 1831, and James Clerk ...

when a conductor attached to a circuit moves in a

magnetic field A magnetic field is a vector field that describes the magnetic influence on moving electric charges, electric currents, and magnetic materials. A moving charge in a magnetic field experiences a force perpendicular to its own velocity and to ...

. It can be used to determine the direction of current in a generator's windings. When a conductor such as a wire attached to a circuit moves through a magnetic field, an

electric current An electric current is a stream of charged particles, such as electrons or ions, moving through an electrical conductor or space. It is measured as the net rate of flow of electric charge through a surface or into a control volume. The moving pa ...

is induced in the wire due to

Faraday's law of induction Faraday's law of induction (briefly, Faraday's law) is a basic law of electromagnetism predicting how a magnetic field will interact with an electric circuit to produce an electromotive force (emf)—a phenomenon known as electromagnetic inducti ...

. The current in the wire can have two possible directions. Fleming's right-hand rule gives which direction the current flows. The right hand is held with the

thumb The thumb is the first digit of the hand, next to the index finger. When a person is standing in the medical anatomical position (where the palm is facing to the front), the thumb is the outermost digit. The Medical Latin English noun for thumb ...

index finger The index finger (also referred to as forefinger, first finger, second finger, pointer finger, trigger finger, digitus secundus, digitus II, and many other terms) is the second digit of a human hand. It is located between the thumb and the mid ...

and

middle finger The middle finger, long finger, second finger, third finger, toll finger or tall man is the third digit of the human hand, located between the index finger and the ring finger. It is typically the longest digit. In anatomy, it is also called ...

mutually perpendicular to each other (at right angles), as shown in the diagram.{{Cite book, title=Hughes Electrical & Electronic Technology, last=Hughes, first=Edward, date=5 April 2016, publisher=Pearson Education Limited, isbn=978-1-292-09304-8, edition=12th, pages=145 * The thumb is pointed in the direction of the motion of the conductor relative to the magnetic field. * The first finger is pointed in the direction of the magnetic field. By convention, it's the direction from North to South magnetic pole. * Then the second finger represents the direction of the induced or generated current within the conductor (from + to −, the terminal with lower

electric potential The electric potential (also called the ''electric field potential'', potential drop, the electrostatic potential) is defined as the amount of work energy needed to move a unit of electric charge from a reference point to the specific point in ...

to the terminal with higher electric potential, as in a voltage source) The bolded letters in the directions above give a mnemonic way to remember the order. Another mnemonic for remembering the rule is the initialism "FBI", standing for Force (or otherwise motion), B the symbol for the magnetic field, and I the symbol for current. The subsequent letters correspond to subsequent fingers, counting from the top: thumb → F; first finger → B; second finger → I. There is also a Fleming's left-hand rule (for

electric motors An electric motor is an electrical machine that converts electrical energy into mechanical energy. Most electric motors operate through the interaction between the motor's magnetic field and electric current in a wire winding to generate force ...

). The appropriately handed rule can be recalled from the letter "g", which is in "right" and "generator". These

mnemonic A mnemonic ( ) device, or memory device, is any learning technique that aids information retention or retrieval (remembering) in the human memory for better understanding. Mnemonics make use of elaborative encoding, retrieval cues, and imag ...

s are named after British engineer

John Ambrose Fleming Sir John Ambrose Fleming FRS (29 November 1849 – 18 April 1945) was an English electrical engineer and physicist who invented the first thermionic valve or vacuum tube, designed the radio transmitter with which the first transatlantic rad ...

, who invented them. An equivalent version of Fleming's right-hand rule is th
left-hand palm rule

References

External links

Diagrams and exercises
Science mnemonics Electromagnetism zh:佛來明右手定則