The Invention of the Incandescent Light Bulb

The Invention of the Incandescent Light Bulb

A team of physicists has discovered an innovation that could save the incandescent light bulb. Their bulb has energy efficiency on par with LED bulbs, longer life and color fidelity.

The incandescent light bulb is a revolutionary invention that produces light by heating a material to a high temperature. Inventors have made many improvements to the incandescent light bulb over time including reducing its energy consumption and increasing its lifespan.

Origins

When an electrical current flows through a filament in the light bulb, electrons and electron holes interact to emit visible light. This happens because electrons are drawn to the hotter parts of the filament.

The first incandescent light bulbs were developed by Humphry Davy, a British chemist, and Alessandro Volta, the namesake of the electric battery. Davy used the voltaic pile to pass electricity through a charcoal strip that glowed, creating the first electric arc lamp.

In 1840 Warren de la Rue enclosed a coiled platinum filament in an evacuated glass tube and passed an electric current through it. This design worked but the high cost of platinum made it impractical for widespread use.

Joseph Wilson Swan started working with carbonized paper filaments in an evacuated bulb in 1850 and, by 1860, was able to produce a constant electric lighting system. He also developed a mercury vacuum pump making it possible to develop a practical light bulb. Edison ultimately won the patent for his light bulb design using a carbon rod in an elongated glass tube, but he continued to refine it throughout his career.

Filament Materials

The filament that lights up a bulb must be able to stand high temperatures as it’s heated by electricity. It must also be resistant to oxidation output speed sensor and evaporation. Tungsten metal is the preferred material, because of its very high melting point, low vapor pressure, tensile strength, and resistance to blackening.

The tungsten filament is often coiled to slow down the rate of evaporation and reduce heat loss. This is why the bulbs we use today are called double-coil lamps.

When electricity passes through a lamp’s filament, it generates visible light, and the heat generated by the filament also emits infrared radiation. This radiated energy is useless to the human eye, but useful to the bulb’s light-emitting mechanism.

The filament’s shape has a major impact on the bulb’s lifespan. The classic straight filament found in most traditional bulbs, for example, disperses the emitted light evenly and has a long life, but is less energy efficient, because it discharges heat in all directions, resulting in wasted energy. A coiled filament, on the other hand, has a shorter lifespan but is more energy-efficient because it carries a lower current density and releases less wattage of unused infrared radiation.

Input Voltage

An incandescent light bulb converts electrical energy into heat and visible light by passing current through a filament of tungsten wire. When the filament is heated to very high temperatures, it emits thermally equilibrated photons in the black body spectrum, giving off a warm white light.

Humphry Davy’s first filament-based electric lamp produced a glow but did not last very long, and it was more than 100 years before inventors had perfected the design to make it work reliably. Today’s bulbs are easy to manufacture, inexpensive and operate well on either AC or DC current.

The filament is housed in an envelope made of a glass container that is usually evacuated or filled with inert gas to reduce evaporation and improve the strength of the glass. A socket at the base provides mechanical and electrical support for the filament and contacts for the electrical current. Less than 5% of the electricity consumed by a standard incandescent light bulb is converted to visible light; most is emitted as invisible infrared radiation. The luminous efficacy of incandescent light bulbs is typically rated at about 1 lumen per watt.

Output Voltage

The amount of light emitted from an incandescent bulb depends on how hot the filament gets. It also depends on the voltage it’s running at. If you operate a bulb at less than its rated voltage it will draw significantly less current and put out less light. Severely under-voltage will produce an orange or reddish glow.

The majority of an incandescent bulb’s power consumption is dissipated as heat. This waste of energy is one reason countries are phasing out standard incandescent bulbs.

Our selection of incandescent light bulbs includes a wide variety of sizes, voltage ratings and degrees of light output. Use the refine options on the left side of the page to narrow your choices and then select the type of bulb you need. Then use the wattage chart to find the bulb that fits your fixture. Remember incandescent light bulb that wattage indicates how much power the bulb consumes, not how bright it is. The brightness is rated in lumens. The higher the wattage, the more light it produces. The brightness of a bulb is also affected by how thick the filament wire is.

Life Expectancy

While they may be very cheap to buy, most light bulbs are very expensive to maintain. They have short lifespans compared to many other types of lighting and are usually sold according to their electrical power consumption rather than their luminous efficacy or lumens per watt (lm/W). Less than five percent of the energy used to heat the filament is converted into visible light; the rest is emitted as invisible infrared radiation.

Incandescent light bulbs are hard-fail, meaning they burn out all at once and cannot be re-lit. They can also be difficult to find in a wide variety of shapes, sizes and wattages as many manufacturers have phased them out in favor of more energy-efficient alternatives like fluorescent lamps or LEDs.

Edison’s initial incandescent bulbs lasted only several hours, but he worked on small improvements to the design until finally creating a bulb that would last for over fourteen hours. Since then, inventors have figured out how to improve the design of bulbs by filling them with inert gases and using tungsten filaments that last longer.