An electrical generator positionable downhole in a well bore includes a tubular housing having a first longitudinal end and a second longitudinal end, the housing having an internal passageway with a plurality of layers. The layers comprise at least a first protective layer, a second protective layer, and an electrically conductive layer positioned between the first and second protective layers. The layers define an internal cavity. A shaft with magnetic inserts is movably positioned in the internal cavity. Electrical current is generated when the shaft is moved. Alternatively, the device may be supplied with electrical power and used as a downhole motor.