Nernst lamp Museum für Energiegeschichte, Hannover AEG (Allgemeine ElektricitätsGesellschaft), Berlin. Model D, c. 1900. Voltage: ? V; current: ? A. Edison E27 base. Brass cylinder, length 55 mm, diameter 43 mm, 16 large slots (15 × 5 mm), 64 small slots; it contains the ballast (iron hydrogen resistor). Globe: 60 mm diameter. Total length of lamp: c. 140 mm. 

Nernst lamp AEG (Allgemeine ElektricitätsGesellschaft), Berlin. Model D, c. 1900. Voltage: ? V; current: ? A. Bayonet base. Brass cylinder, length 55 mm, diameter 43 mm, 16 large slots (15 × 5 mm), 64 small slots; it contains the ballast (iron hydrogen resistor). Globe: 60 mm diameter. Total length of lamp: 142 mm. The heater and the glower are missing. 

Porcelain base Small diameter 22 mm, large diameter 42 mm, length 43 mm. Inside the base there is the solenoid which turns off the heater. 

Solenoid (photograph taken from AEG model B) Length of coil 15 mm. Resistance c. 8 ohm. 

Ballast (iron hydrogen resistor) (taken from AEG model B) Two thin iron filaments in an atmosphere of hydrogen gas. The resistance of iron increases with temperature (PTC, positive temperature coefficient), in particular at high temperature when the wire is glowing red. Length 42 mm, diameter 17 mm. Resistance c. 50 ohm at room temperature. 

Mica plate Size 25 × 13 mm Stamped "AEGMA" (Allgemeine ElektricitätsGesellschaft). 
Revised 20050806