The flick of a switch - and in a moment the dark room changed, details of the smallest elements of the interior became visible. Thus, energy from a small device instantly spreads, filling everything around with light. What makes us create such powerful radiation? The answer is hidden in the name of the lighting device, which is called an incandescent lamp.
History of the first lighting elements
The origins of the first incandescent lamps date back to the beginning of the XIX century. Rather, the lamp appeared a little later, but they tried to observe the effect of the glow of platinum and coal rods under the influence of electric energy. Scientists had two difficult questions:
- finding materials of high resistance that can heat up under the influence of current to the state of light emission;
- prevention of rapid combustion of the material in the air.
The most fruitful in this area were the research and invention of the Russian scientist Alexander Nikolayevich Lodygin and the American Thomas Edison.
Lodygin suggested using carbon rods, which were in an airtight flask, as an incandescent element. The design drawback was the difficulty of pumping air, the remains of which contributed to the rapid combustion of the rods. But still, his lamps burned for several hours, and developments and patents became the basis for creating more durable devices.
The American scientist Thomas Edison, having familiarized himself with the work of Lodygin, made an effective vacuum flask in which he placed a charcoal thread from bamboo fiber. Edison also provided the lamp base with a threaded connection inherent in modern lamps, and invented many electrical components, such as a plug, fuse, rotary switch and much more. The efficiency of Edison's incandescent lamp was small, although it could work up to 1000 hours of time and got practical application.
Subsequently, instead of coal elements, it was proposed to use refractory metals. Tungsten filament used in modern incandescent lamps was also patented by Lodygin.
The device and principle of operation of the lamp
The design of an incandescent lamp has not fundamentally changed for more than a hundred years. It includes:
- A sealed flask that limits the working space and is filled with an inert gas.
- A basement that has a spiral shape. It serves to hold the lamp in the cartridge and electrically connect it to live parts.
- Conductors that conduct current from the base to the spiral and hold it.
- An incandescent spiral, the heating of which creates the emission of light energy.
When an electric current passes through a spiral, it instantly heats up to the highest temperatures up to 2700 degrees. This is due to the fact that the spiral has a large resistance to current and to overcome this resistance a lot of energy is spent, which is released as heat. Heat heats the metal (tungsten), and it begins to emit photons of light. Due to the fact that the flask does not contain oxygen, tungsten does not oxidize during heating, and it does not burn out. Inert gas keeps particles of hot metal from evaporating.
What is the efficiency of an incandescent lamp
The efficiency shows what percentage of the energy spent is converted into useful work and which is not. In the case of an incandescent lamp, the efficiency is low, since only 5-10% of the energy goes to the emission of light, the rest is released as heat.
The efficiency of the first incandescent lamps, where the carbon rod was the glowing body, was even lower compared to modern devices. This is due to additional losses due to convection. Spiral filaments have a lower percentage of these losses.
The efficiency of an incandescent lamp directly depends on the heating temperature of the coil. As a standard, a 60 W lamp spiral heats up to 2700 º, while the efficiency is only 5%. It is possible to increase the heating value to 3400 º, increasing the voltage, but this will reduce the life of the device by more than 90%, although the lamp will lighten brighter and the efficiency will increase to 15%.
It is wrong to think that an increase in lamp power (100, 200, 300 W) leads to an increase in efficiency only because the brightness of the device has increased. The lamp began to shine brighter due to the greater power of the spiral itself, and as a result of greater light output. But energy costs have also increased. Therefore, the efficiency of a 100 W incandescent lamp will also be in the range of 5-7%.
Varieties of incandescent lamps
Incandescent lamps come in various designs and functional purposes. They are divided into lighting devices:
- General application. These include lamps for domestic use of different capacities, designed for a mains voltage of 220 V.
- Decorative performance. They have non-standard types of flasks in the form of candles, spheres and other shapes.
- Illumination type. Low-power, color-coated lamps to create colorful illuminations.
- Local destination. Safety voltage devices up to 40 V. Used on production tables, for lighting workplaces of machines.
- With a mirror coating. Lamps that create directional light.
- Signal type. Serve to work in the dashboards of various devices.
- For transport. A wide range of lamps of increased wear resistance and reliability. They are characterized by a convenient design that requires quick replacement.
- For floodlights. High power lamps up to 10,000 watts.
- For optical devices. Lamps for film projectors and similar devices.
- Switching Used as segments of an indicator for digital display of measuring instruments.
The positive and negative sides of lamps with a body
Incandescent lighting devices have their own characteristics. The positive include:
- instant ignition of the spiral;
- environmental safety;
- small sizes;
- reasonable price;
- the ability to create devices of different power and the magnitude of the operating voltage of both alternating and direct current;
- universality of application.
To the negative:
- low efficiency of an incandescent lamp;
- sensitivity to power surges, reducing the life of the device;
- short working hours not exceeding 1000;
- fire hazard of lamps due to strong heating of the bulb;
- fragility of the structure.
Other types of lighting
There are lighting lamps, the principle of which is fundamentally different from the operation of incandescent lamps. These include discharge lamps and LED lamps.
There are a large number of arc or gas discharge lamps , but all of them are based on the glow of gas when an arc arises between the electrodes. The glow occurs in the ultraviolet spectrum, which is then converted into the visible to the human eye by passing through a phosphor coating.
The process taking place in a gas discharge lamp includes two stages of work: creating an arc discharge and maintaining the ionization and glow of the gas in the bulb. Therefore, all types of such lighting devices have a current control system. Luminescent devices have a higher efficiency compared to the efficiency of an incandescent lamp, but are unsafe because they contain mercury vapor.
LED lighting devices are the most advanced systems. The efficiency of an incandescent lamp and an LED lamp are not comparable. In the latter, it reaches 90%. The principle of operation of the LED is based on the glow of a certain type of semiconductor under the influence of voltage.
What the incandescent lamp does not like
The life of a conventional incandescent lamp will be reduced if:
- The voltage in the network is constantly overstated from the rated voltage for which the lighting device is designed. This is due to an increase in the working temperature of the filament body and, as a consequence, increased evaporation of the metal alloy, leading to its failure. Although the efficiency of the incandescent lamp will be greater.
- Shake the lamp sharply during operation. When the metal is heated to a state close to melting, and the distance between the turns of the spiral is reduced due to expansion of the substance, any mechanical, sudden movement can lead to an invisible interturn closure. This reduces the overall resistance of the spiral to current, contributes to its greater heating and rapid burnout.
- Moisture will get on the heated flask. At the point of impact, a temperature difference occurs, which produces the destruction of the glass.
- Touch the bulb of the halogen lamp with your fingers . A halogen lamp is a type of incandescent lamp, but has significantly greater light and heat output. When you touch the flask, an invisible greasy spot from the finger remains. Under the influence of temperature, fat burns out, forming carbon deposits, which prevents heat transfer. As a result, the glass begins to melt at the point of contact and can burst or swell, disrupting the gas regime inside, which leads to burnout of the spiral. Efficiency halogen incandescent lamps are higher than ordinary ones.
How to replace a lamp
If the lamp burns out, but the bulb does not collapse, then you can replace it after complete cooling. In this case, turn off the power. When screwing the lamp, the eyes do not need to be directed in its direction, especially if it is not possible to turn off the electricity.
When the flask burst, but retained its shape, it is advisable to take a cotton cloth, fold it in several layers and, clasping a lamp with it, try to remove the glass. Next, with pliers with insulated handles, carefully unscrew the base and screw in a new lamp. All operations must be carried out with the power supply turned off.
Conclusion
Despite the fact that the efficiency of an incandescent lamp is few percent and it has more and more competitors, it is relevant in many areas of life. There is even the oldest light bulb, continuously working for more than a hundred years. Is this not a confirmation and perpetuation of the genius of the thought of a person striving to change the world?