Download Right-Hand Rules

Right-Hand Rules: A Guide to finding the
Direction of the Magnetic Force
Fmagnetic - The force a magnetic field exerts on a moving charge
When a charge is placed
in a magnetic field, that
charge experiences a
magnetic force; when
two conditions exist:
1) the charge is moving
relative to the magnetic
field,
2) the charge's velocity
has a component
perpendicular to the
direction of the
magnetic field
The Right-Hand Rules apply to positive charges or positive (conventional) current
When using the Right-Hand Rules, it is
important to remember that the rules
assume charges move in a conventional
current (the hypothetical flow of positive
charges). In order to apply either RightHand Rule to a moving negative charge,
the velocity (v) of that charge must be
reversed--to represent the analogous
conventional current.
Making illustrations of magnetic field and charge
interactions in 3D
Because the force exerted
on a moving charge by a
magnetic field is
perpendicular to both the
the velocity of the charge
and the direction of the
field, making illustrations
of these interactions
involves using the two
symbols on the left to
denote movement into or
out of the plane of the page.
Right-Hand Rule #1 (RHR #1)
Right-Hand Rule #1 determines the directions of magnetic force, conventional current
and the magnetic field. Given any two of theses, the third can be found.
Using your right-hand:
point your index finger in the
direction of the charge's velocity, v,
(recall conventional current).
Point your middle finger in the
direction of the magnetic field, B.
Your thumb now points in the
direction of the magnetic force,
Fmagnetic.
Right-Hand Rule #2 (RHR #2)
a. Right-Hand Rule #2 determines the direction of the magnetic field
around a current-carrying wire and vice-versa. It is used to find the
direction of the field produced by an electromagnet
Using your right-hand:
Curl your fingers into a half-circle
around the wire, they point in the
direction of the magnetic field, B
Point your thumb in the direction of
the conventional current.
Right-Hand Rule #3 (RHR #3)
Used to find the direction of the force on a current-carrying wire in a magnetic field.
Using your right-hand:
Hold out your hand like a stop gesture.
Thumb (A) shows direction of current or direction of an
individual charge. Fingers (B) point in the direction of
the magnetic field. The palm (C) shows the direction of
force (FB) or push.
F = ILB sin where L = length of wire
have perpendicular
I is current
B is magnetic field
Use only when you don’t
perpendicular directions.
Applying the Right-Hand Rules:
The Right-Hand Rules give only the direction of the magnetic field. In order to determine the
strength of a magnetic field, some useful mathematical equations can be applied.
For a long, straight wire, the
magnetic field, B is:
B = oI / 2r (bunny equation);
, r is the radial distance from
the wire in meters, and I is the
current in amperes.
For a single loop of wire, the
magnetic field, B through the center
of the loop is:
B = oI / 2R;
where,
o is the permeability of free space,
and R is the radius of the circular
loop of wire, measured in meters.
Both the fields for a coil of wire and
a solenoid can be constructed from
this equation.