Powering a Light Bulb With a Battery
Q:How can I power a lightbulb with a battery?
A: Simply connect the battery's positive terminal to one of the electrical contacts on your light bulb and its negative terminal to the other. Many lightbulbs feature one electrical contact with screw threads and a circular dot on the base for the second contact. Metal prongs will protrude from other bulbs. By soldering wires on, it is very difficult to get adequate electrical contact with batteries and lamps. The spring contacts in flashlights function considerably better (but even those sometimes cause issues).
It's critical to choose a bulb whose output corresponds to that of your battery. The current going through the bulb will be tiny and the filament won't grow hot enough to clearly light if the battery voltage is too low. The filament will get overheated and vaporise if the battery has a voltage that is too high.
Standard lights need a voltage of around 120 V to operate, which is an uncommon range for batteries. Ordinary torch lights need roughly 3V to operate, which is simple to acquire by connecting two batteries in series. Typically, automotive bulbs are designed to operate with 12V, which is the output of an automobile battery or eight conventional battery cells connected in series.
Using a lower voltage would seem like it would just slightly dim the light, but in reality, the impact is far more dramatic. First, until the voltage is high enough for the bulb to heat up and raise its resistance, the heating power in the bulb is proportional to the square of the voltage. Second, until the filament temperature approaches the normal operating temperature, the quantity of visible light generated by the bulb is almost nothing. Therefore, employing one fourth of the electricity will result in substantially less light production than one fourth. The bulb will glow orangeish if the voltage is a little bit too low since it can still emit certain colours of light but not blue light.
Even if you provide the same amount of heating power as a 60 W bulb, you probably don't glow very much. That's because you don't have enough heat to emit visible light. Infrared, which our eyes can sense indirectly but not directly, is the light you do emit.
