If you are a science student and learning physics and
especially motors, then understanding Fleming’s Left Hand Rule is one of the
things that you must learn and get good at. Fleming’s Left Hand Rule is one of
the rules and principles that will serve you for the rest of your life.
Fleming's
left-hand rule (for motors), and Fleming's right-hand rule (for generators)
are a pair of visual mnemonics. They were originated by John Ambrose Fleming,
in the late 19th century, as a simple way of working out the direction of
motion in an electric motor, or the direction of electric current in an
electric generator.
Process
·
Fleming's left hand rule (for electric motors)
shows the direction of the thrust on a conductor carrying a current in a
magnetic field.
·
The left hand is held with the thumb, index
finger and middle finger mutually at right angles. It can be recalled by
remembering that "motors drive on the left, in Britain anyway."
·
The First finger represents the direction of the
magnetic Field. (north to south)
·
The Second finger represents the direction of
the Current (the direction of the current is the direction of conventional
current; from positive to negative).
·
The Thumb represents the direction of the Thrust
or resultant Motion.
Effect
When a wire carrying an electric current is moved in a
magnetic field of a magnet the magnetic field induced by the wire reacts with
the magnetic field of the magnet causing the wire to move outwards. Fleming's
left hand rule helps you to predict the movement.
First finger - direction of magnetic field (N-S)
Second finger - direction of current (positive to negative)
Thumb - movements of the wire
When a coil of wire carrying a current is placed in a
magnetic field the coil turns.
This is called the motor effect.
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