where
F = the force (in newtons[10])
q = the charge on the electron (1.6 × 10⁻¹⁹ coulomb)
v = the wire’s velocity (in meters per second)
B = the magnetic field strength (in webers per square meter[10])
The surge of electrons along the length of the wire sets up a voltage
difference across the ends of the wire. A generator uses this difference
to convert the kinetic energy of the moving wire or armature into
electrical energy. The wire is kept spinning by the shaft which is
connected to a turbine driven by steam or water.
Let us try to eliminate the moving part, the generator armature. What we
need is a moving conductor that has no shaft, no bearings, no wearing
parts. The substance that meets these requirements is the plasma.
Examine Figure 9a. The MHD generator substitutes a moving, conducting
gas for the wires. Under the influence of an external magnetic field,
the conduction electrons move through the plasma to one side of the duct
which carries electrical power away to the load.
The MHD generator gets its energy from an expanding, hot gas; but,
unlike the turbogenerator, the heat engine and generator are united in
the static duct. The gradual widening of the duct shown in Figure 9a
reflects the lower pressure, cooler plasma at the duct’s end. Some of
the plasma’s thermal energy content has been tapped off by the duct’s
electrodes as electrical power.