13.2 CHAPTER 13. ELECTRODYNAMICS
DEFINITION: Motor
An electric motor converts electrical energy intomechanical energy.If one were to place a moving charged particle ina magnetic field, it would feel a force
called the Lorentz force.
DEFINITION: The Lorentz Force
The Lorentz force is the force experienced by a moving charged particle
in a magnetic field andcan be described by:F = q× v× Bwhere
F is the force (in newtons, N)
q is the electric charge (incoulombs, C)
v is the velocity of the charged particle (in m.s−^1 ) and
B is the magnetic field strength (in teslas, T).Current in a conductorconsists of moving charges. Therefore, a current carrying coil
in a magnetic field willalso feel the Lorentz force. For a straight current carrying wire
which is not moving:
F = I× L× B
where
F is the force (in newtons, N)
I is the current in the wire (in amperes, A)
L is the length of the wirewhich is in the magneticfield (in m) and
B is the magnetic field strength (in teslas, T).
The direction of the Lorentz force is perpendicular to both the directionof the flow of
current and the magnetic field and can be foundusing the Right Hand Rule as shown
in the picture below. Use your right hand; your thumb points inthe direction of the
current, your first fingerin the direction of the magnetic field and your third finger will
then point in the direction of the force.