Electricity and Magnetism
DEM40 - Generator
- To study both alternating and direct currents produced by a generator.
- Simple Generator (Stansi)
- OHP ammeter (50-0-50 mA DC scale)
- Ttwo power supplies (Eico)
- Knife switch, DPDT
The above apparatus and schematic are used for both DEM40 and DEM41.
The hand-driven generator employs an electromagnet to produce the necessary
magnetic field. The brushes are interchangeable from DC (commutator) to
AC (slip rings). On DC the OHP shows a unidirectional current with magnitude
and direction being a function of armature velocity and direction of rotation.
On AC armature rotation produces a bipolar, sinusoidal current, occupying
both halves of the center-zero ammeter.
- Turn the armature slowly to observe the effects since mechanical
inertia within the ammeter movement plus the effects of damping can
- The DPDT knife switch must be returned to the "center-off"
position to avoid overheating the field coil.
- Demonstrations DEM40 and DEM41 are very conveniently presented together
as one package, with selection made via the knife switch.