Transcript Right-hand rule

RHR
• Direction of force
• See also: Right-hand rule
• The direction of force on a charge or a current can be
determined by a mnemonic known as the right-hand rule.
See the figure on the left. Using the right hand and pointing
the thumb in the direction of the moving positive charge or
positive current and the fingers in the direction of the
magnetic field the resulting force on the charge points
outwards from the palm. The force on a negatively charged
particle is in the opposite direction. If both the speed and the
charge are reversed then the direction of the force remains
the same. For that reason a magnetic field measurement (by
itself) cannot distinguish whether there is a positive charge
moving to the right or a negative charge moving to the left.
(Both of these cases produce the same current.) On the
other hand, a magnetic field combined with an electric field
can distinguish between these, see Hall effect below.
• An alternative mnemonic to the right hand rule is Fleming's
left hand rule.
Hall effect
• Main article: Hall effect
• The charge carriers of a current carrying conductor
placed in a transverse magnetic field experience a
sideways Lorentz force; this results in a charge
separation in a direction perpendicular to the current and
to the magnetic field. The resultant voltage in that
direction is proportional to the applied magnetic field.
This is known as the 'Hall effect'.
• The Hall effect is often used to measure the magnitude
of a magnetic field. It is used as well to find the sign of
the dominant charge carriers in materials such as
semiconductors (negative electrons or positive holes).