Tungsten Lamps are made for voltages as low as one and one-half, and will light on one cell of dry battery. The range of voltages is quite wide and varied. A few of the most common sizes are given below:
MINIATURE TUNGSTEN BATTERY LAMPS
1.5 volts. for one dry cell
2.5 volts. for two-cell flashlight battery
2.8 volts. for two-cell flashlight battery
3.5 volts. for three-cell flashlight battery
3.8 volts. for three-cell flashlight battery
4 volts. 4 candle-power
6 volts. 2 candle-power
6 volts. 4 candle-power