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It turns out that a body heated by an electric current can not only emit heat, but also glow. The first light sources operated precisely on this principle. Let's look at how an incandescent lamp, the most widely used lighting device in the world, works. And, although over time it will have to be completely replaced by compact fluorescent (energy-saving) and LED light sources, humanity will not be able to do without this technology for a long time.

Incandescent lamp design

The main element of the light bulb is a spiral made of a refractory material - tungsten. To increase its length and, accordingly, resistance, it is twisted into a thin spiral. It is not visible to the naked eye.

The spiral is mounted on supporting elements, the outermost of which serve to connect its ends to the electrical circuit. They are made of molybdenum, the melting point of which is higher than the temperature of the heated coil. One of the molybdenum electrodes is connected to the threaded part of the base, and the other to its central terminal.

Molybdenum holders hold the tungsten helix

Air has been pumped out of a flask made of glass. Sometimes, instead of air, an inert gas is pumped inside, for example, argon or its mixture with nitrogen. This is necessary to reduce the thermal conductivity of the internal volume, as a result of which the glass is less susceptible to heating. Additionally, this measure prevents oxidation of the filament. When making a lamp, air is pumped out through part of the bulb, which is then hidden by the base.

The principle of operation of an incandescent lamp is based on heating its filament by electric current to a temperature at which it begins to emit light into the surrounding space.

Incandescent lamps can be manufactured with a power from 15 to 750 W. Depending on the power, different types of threaded sockets are used: E10, E14, E27 or E40. For decorative, signal and backlight lamps, BA7S, BA9S, BA15S sockets are used. When installed, such products are stuck inside the cartridge and rotated 90 degrees.

In addition to the usual pear-shaped shape, decorative lamps are also produced in which the bulb is shaped like a candle, drop, cylinder, or ball.

A lamp with a bulb that does not have a coating glows with a yellowish light, the composition most reminiscent of sunlight. But when special coatings are applied to the inner surface of the glass, it can become matte, red, yellow, blue or green.

The design of a reflective incandescent lamp is of interest. A reflective layer is applied to part of its bulb. As a result, due to reflection from it, the light flux is redistributed in one direction.

Advantages of incandescent lamps

The most important advantage in favor of using incandescent light bulbs is the ease of their manufacture and, accordingly, the price. It’s impossible to think of a simpler lighting device.

Lamps are manufactured in a wide range of wattages and overall dimensions. All other modern light sources contain devices that convert the supply voltage to the value necessary for their operation. Although they manage to squeeze them into the standard overall dimensions of a light bulb, the design becomes more complicated and the number of parts in the device increases. And this does not always improve cost and reliability indicators. The incandescent lamp switching circuit does not require any additional elements.

LED lamps have replaced conventional lamps as portable devices: portable light sources powered by batteries and rechargeable batteries. With the same light output, they consume less current, and the overall dimensions of the LED are even smaller than the bulbs previously used in flashlights. And they work more successfully as part of Christmas tree garlands.

It is worth noting another advantage inherent in incandescent light bulbs - their luminescence spectrum is closest to that of the sun than that of all other artificial light sources. And this is a big plus for vision, because it is adapted specifically to the sun, and not to monochrome LEDs.

Due to the thermal inertia of the heated filament, the light from it practically does not pulsate. The same cannot be said about the radiation from other devices, especially luminescent ones, which use a regular inductor rather than a semiconductor circuit as a ballast. And electronics, especially cheap ones, do not always suppress ripple from the network properly. This also affects vision.

But not only health can be damaged by the pulsating nature of the operation of semiconductor devices used in modern light bulbs. Their massive use leads to a sharp change in the shape of the current consumed from the network, which ultimately affects the shape of the voltage. It changes so much in relation to the original (sinusoidal) that it affects the quality of operation of other electrical appliances in the network.

Disadvantages of incandescent lamps

A significant drawback of incandescent light bulbs, which shortens their service life, is its dependence on the value of the supply voltage. As the voltage increases, the filament wears out faster. Lamps are produced for different values ​​of this parameter (up to 240 V), but at the nominal value they shine worse.

A decrease in voltage leads to a sharp change in the intensity of the glow. And vibrations have an even worse effect on the lighting device; with sudden fluctuations, the lamp can burn out.

But the worst thing is that the filament is designed to operate for a long time in a heated state. When heated, its resistivity increases. Therefore, at the moment of switching on, when the thread is cold, its resistance is much less than that at which the glow occurs. This leads to an inevitable current surge at the moment of ignition, leading to the evaporation of tungsten. The greater the number of switches, the shorter the lamp will last.

Devices for smooth starting or that allow you to adjust the brightness of the glow over a wide range help correct the situation.

The most important disadvantage of incandescent light bulbs is their low efficiency. The overwhelming majority of electricity (up to 96%) is spent on useless heating of the surrounding air and radiation in the infrared spectrum. Nothing can be done about this - this is the principle of operation of an incandescent lamp.

Well, one more thing: the glass of the flask is easy to break. But unlike compact fluorescent lamps, which contain a small amount of mercury vapor inside, a broken incandescent lamp, apart from a possible cut, does not threaten the owner in any way.

Halogen lamps

The cause of incandescent lamp burnout is the gradual evaporation of the tungsten from which the filament is made. It becomes thinner, and then the next current surge when turned on melts it at its thinnest point.

Halogen lamps filled with bromine or iodine vapor are designed to eliminate this drawback. When burned, evaporated tungsten combines with halogen. The resulting substance is not able to deposit on the walls of the flask or other relatively cold internal surfaces.

Near the filament, tungsten, under the influence of temperature, is removed from the connection and returned to its place.

The use of halogens solves another problem: the temperature of the coil can be raised, increasing the luminous output and reducing the size of the lighting device. Therefore, at the same power, the dimensions of halogen lamps are smaller.

Incandescent lamp is an electric light source that emits light flow as a result of heating a conductor made of refractory metal (tungsten). Tungsten has the highest melting point of all pure metals (3693 K). The filament is located in a glass flask filled with an inert gas (argon, krypton, nitrogen). Inert gas protects filaments from oxidation. For low-power incandescent lamps (25 W), vacuum flasks are made that are not filled with inert gas. The glass bulb prevents the negative effects of atmospheric air on the tungsten filament.

To calculate the room illumination, you can use the room illumination calculator.

Types of incandescent lamps.

Incandescent lamps are divided into:

• Vacuum;
• Argon (nitrogen-argon);
• Krypton (+10% brightness from argon);
• Xenon (2 times brighter than argon);
• Halogen (composition I or Br, 2.5 times brighter than argon, long service life);
• Halogen with two flasks (improved halogen cycle due to better heating of the inner flask);
• Xenon-halogen (composition Xe + I or Br, up to 3 times brighter than argon);
• Xenon-halogen with IR reflector;
• Filament with a coating that converts infrared radiation into the visible range. (new)

Advantages and disadvantages of incandescent lamps.

Advantages:

• low cost;
• instant ignition when turned on;
• small overall dimensions;
• wide power range.

Flaws:

• high brightness (negatively affects vision);
• short service life - up to 1000 hours;
• low efficiency. (only a tenth of the electrical energy consumed by the lamp is converted into visible light flux) the rest of the energy is converted into heat.

Characteristics of incandescent lamps.

Light flow is a physical quantity that characterizes the amount of “light” power in the corresponding radiation flux.

Luminous output- this is the ratio of the luminous flux emitted by a source to the power it consumes, measured in lumens per watt (lm/W). It is an indicator of the efficiency and economy of light sources.

Lumen is a unit of measurement of luminous flux, luminous quantity.

Luminous flux and luminous efficiency of incandescent lamps.

Comparative table of the ratio of luminous flux to power consumption of various types of lamps.

Characteristics of different types of lamps in terms of light transmission.

• LN- incandescent lamps;
• GLN- halogen lamps;
• CFL- compact fluorescent lamps;
• MGL- metal halide lamps;
• LL- fluorescent lamps;
• LEDs- LED bulbs.

Characteristics of various types of incandescent lamps.

Lamp voltage - U, Volt;

Lamp power - W, W;

Luminous flux - Lm, Lumen.

General purpose incandescent lamps (standard).

General purpose incandescent lamps (minions).

General purpose incandescent lamps (mirror).

General purpose incandescent lamps (matte).

Schemes for switching on incandescent lamps.

Wiring diagram for switching on a single-lamp lamp with a socket.

Schematic diagram of switching on one lamp with a switch and a plug socket.

Today it is difficult to imagine people's lives without an electric lamp. This fairly simple device is used to illuminate various rooms and streets. There are a large number of types of light bulbs, differing in luminous power and operating principle. Lately, users are increasingly paying attention to energy-saving devices, but the conventional incandescent lamp is in no hurry to lose ground.

Operating principle

The operating principle of an incandescent lamp is quite simple, like the design of this device. An electric current passes through a refractory conductor and heats it to a high temperature. It should be noted that the heating temperature depends on the voltage supplied to the device. According to Planck's law, a heated conductor is capable of generating electromagnetic waves.

The higher the temperature, the shorter the wavelength of the emitted radiation. Waves of the visible spectrum appear when the conductor is heated to several thousand degrees on the Kelvin scale. If the spiral of an electric light bulb is heated to 5000 K, it will glow with neutral light (similar to what the Sun emits). As the temperature decreases, the color of the glow will begin to change first to yellow and then to red.

In lamps, the predominant part of the energy is transformed into heat and only a small amount is converted into luminous flux. It should also be remembered that the human visual organs are capable of perceiving only a certain range of light waves. To increase the illumination of the room, you have to increase the temperature of the coil. However, this is only possible up to a certain point, which is limited by the properties of the conductor material.

Thus, The maximum temperature of the light bulb is 3410 degrees on the Celsius scale. Further heating of tungsten will lead to deformation and melting of the material. However, even this temperature can only be achieved under certain environmental conditions. If tungsten comes into contact with oxygen, it turns into oxide. When the air is pumped out of the flask, it will be possible to create a lamp with a maximum power of 25 W. More powerful devices contain inert gases in the flask.

Design Features

Although the lamps differ in design, they have three common elements - leads, conductor and glass bulb. Some special purpose devices may not have a base because they use a different type of holder. Also sometimes a ferronickel fuse is built into light bulbs. Most often, it is mounted in a leg, so after the conductor fails, the bulb is not destroyed.

When the filament breaks, an electric arc appears, which melts the remaining material. The substance in the molten state falls onto the glass container and can damage its integrity. The fuse can prevent the spiral from melting. However, this technology has not become widespread due to its low efficiency.

If we talk about what a light bulb consists of, then it is necessary to note the main design elements. These include:

• a flask made of glass;
• radiating conductor;
• electrodes;
• base;
• gas environment;
• radiating conductor holders.

Flask and gas environment

Thanks to the glass container, the filament is protected from the oxidation process that occurs when the emitting conductor material interacts with oxygen. The first electric incandescent lamps were produced with a vacuum bulb. Currently, only low-power devices are produced using this technology. To produce more powerful devices, a nitrogen-argon mixture or argon alone is most often used. Also, the bulbs of some lamps may contain xenon or krypton. The thermal emission rate of the filament material depends on the molar mass of the gas.

A separate group are halogen light bulbs, the glass container of which is filled with halogen gas. When heated, the material of the radiating conductor evaporates and reacts with these gases. The substance obtained during the chemical process is quickly broken down under the influence of high temperature and returned to the filament. As a result, not only the efficiency of the device increases, but also its service life increases.

Radiating conductor

The shape of the filament can be any and depends on the specifics of the device. Most often, the conductor in a regular light bulb has a round cross-section, but you can also find a strip cross-section. It should be noted that Even coal was used in the first lamps, capable of heating up to a temperature of 3559 degrees Celsius. However, in modern devices the main filament material is tungsten.

This element can also be made of an osmium-tungsten alloy. The choice of the type of spiral is not random, since its dimensions depend on this. Modern lamps can use bi-spirals and even tri-spirals. They are obtained by repeated twisting. This allows you to increase the efficiency of the device by reducing heat dissipation.

Lamp base

This element is standardized and has a certain shape and dimensions. As a result, you can easily replace the light bulb after it fails. . Today, devices with an E14 base are most often used., E27, and also E40. Deciphering this marking is extremely simple - the numbers after the letter E indicate the outer diameter of the element.

Since there are now a large number of types of lamps, some of them differ in the design of the base. For example, there are devices that are held in a socket due to friction. It should also be noted that the base in an incandescent lamp device performs the following functions:

• connects several elements;
• represents one of the contacts;
• allows you to securely mount the device in the socket.

Advantages and disadvantages

All technical devices have not only advantages, but also disadvantages. Incandescent light bulbs are no exception.

Positive traits

One of the main advantages of these devices is their simplicity of design, which makes the cost of the product low. Nowadays you can easily purchase a device of the desired power and dimensions. An equally important advantage of classic light bulbs is the glow spectrum of their emitting element. Since it is as close as possible to sunlight, it cannot negatively affect the organs of vision.

A heated filament has thermal inertia, so the light emitted by it is practically free of pulsation. This distinguishes conventional incandescent light bulbs from other types of products (for example, fluorescent lamps). No harmful substances are used in the production of these devices, so special technologies are not required for their disposal.

Negative properties

One of the main disadvantages of the devices can be considered the dependence on the supply voltage. If it increases and exceeds permissible limits, then the spiral wears out quickly. When the voltage drops, the luminous flux emitted by the device also decreases.

In addition, it should be remembered that the radiating element is designed to operate over a long period of time. The resistance indicator of a cold spiral is significantly lower compared to the operating mode.

Because of this, at the moment of switching on, a strong jump in current strength occurs, which leads to evaporation of the filament material. Thus, the service life of the device depends on the number of starts.

However, this drawback can be combated by using special soft start devices - dimmers. They can also be used to adjust the luminous flux over a fairly wide range.

The most serious disadvantage of incandescent lamps is their low efficiency. The bulk of the electricity is converted into heat, which is dissipated in the environment. Nowadays, LED lamps are increasingly used to save on electricity.

The Planck function has a maximum, the position of which on the wavelength scale depends on temperature. This maximum shifts with increasing temperature towards shorter wavelengths (Wien's displacement law). To obtain visible radiation, the temperature must be on the order of several thousand degrees, ideally 5770 (the temperature of the surface of the Sun). The lower the temperature, the lower the proportion of visible light and the more “red” the radiation appears.

36 W incandescent lamp

The incandescent lamp converts part of the electrical energy consumed into radiation, while part is lost as a result of the processes of thermal conductivity and convection. Only a small fraction of the radiation lies in the region of visible light, the main share comes from infrared radiation. To increase the efficiency of the lamp and obtain the most “white” light, it is necessary to increase the temperature of the filament, which in turn is limited by the properties of the filament material - the melting point. The ideal temperature of 5770 K is unattainable, because at this temperature any known material melts, breaks down and ceases to conduct electric current. Modern incandescent lamps use materials with maximum melting points - tungsten (3410 °C) and, very rarely, osmium (3045 °C).

At practically achievable temperatures of 2300-2900 °C, the light emitted is far from white and not daylight. For this reason, incandescent light bulbs emit light that appears more "yellow-red" than daylight. To characterize the quality of light, the so-called Colorful temperature .

In ordinary air at such temperatures, tungsten would instantly turn into oxide. For this reason, the tungsten filament is protected by a glass bulb filled with a neutral gas (usually argon). The first lamps were made with evacuated bulbs. However, in a vacuum at high temperatures, tungsten quickly evaporates, making the filament thinner (which leads to its rapid burnout) and darkening the glass bulb when deposited on it. Later, flasks began to be filled with chemically neutral gases. Vacuum flasks are now used only for low-power lamps.

Design

An incandescent lamp consists of a base, contact conductors, a filament, a fuse and a glass bulb filled with a buffer gas and protecting the filament from the environment.

Flask

The glass bulb protects the thread from combustion in the surrounding air. The dimensions of the flask are determined by the deposition rate of the filament material. Higher power lamps require larger bulbs so that the deposited filament material is distributed over a larger area and does not have a strong effect on transparency.

Buffer gas

The bulbs of the first lamps were evacuated. Modern lamps are filled with a buffer gas (except for low-power lamps, which are still made vacuum). This reduces the rate of evaporation of the filament material. Heat losses arising due to thermal conductivity are reduced by choosing a gas with, if possible, the heaviest molecules. Mixtures of nitrogen and argon are an accepted compromise in terms of cost reduction. More expensive lamps contain krypton or xenon (molar masses: nitrogen: 28.0134 /mol; argon: 39.948 /mol; krypton: 83.798 /mol; xenon: 131.293 /mol)

Filament

Double filament incandescent lamp (Osram 200 W) with contact conductors and filament holders

Since the filament is at room temperature when turned on, its resistance is an order of magnitude less than the operating resistance. Therefore, when turned on, a very large current flows (ten to fourteen times the operating current). As the filament heats up, its resistance increases and the current decreases. Unlike modern lamps, early incandescent lamps with carbon filaments worked on the opposite principle when turned on - when heated, their resistance decreased and the glow slowly increased.

In flashing lamps, a bimetallic switch is built in series with the filament. Due to this, such lamps operate independently in flashing mode.

Base

In order to open the circuit when an arc ignites and prevent overload of the supply circuit, a fuse is provided in the lamp design. It is a piece of thin wire and is located in the base of an incandescent lamp. For household lamps with a rated voltage of 220, such fuses are usually rated for a current of 7.

Efficiency and durability

Durability and brightness depending on operating voltage

Almost all the energy supplied to the lamp is converted into radiation. Losses due to thermal conductivity and convection are small. However, only a small range of wavelengths of this radiation is accessible to the human eye. The bulk of the radiation lies in the invisible infrared range and is perceived as heat. The efficiency of incandescent lamps reaches its maximum value of 15% at a temperature of about 3400. At practically achievable temperatures of 2700, the efficiency is 5%.

As the temperature increases, the efficiency of an incandescent lamp increases, but at the same time its durability decreases significantly. At a filament temperature of 2700, the lamp life is approximately 1000 hours, at 3400 only a few hours. As shown in the figure on the right, when the voltage increases by 20%, the brightness doubles. At the same time, the lifetime is reduced by 95%.

Reducing the supply voltage, although it reduces efficiency, but increases durability. So, lowering the voltage by half (for example, when connected in series) greatly reduces the efficiency, but it increases the lifetime by almost a thousand times. This effect is often used when it is necessary to provide reliable emergency lighting without special brightness requirements, for example, on staircase landings. Often, for this purpose, when powered by alternating current, the lamp is connected in series with a diode, due to which current flows into the lamp only during half the period.

The limited lifetime of an incandescent lamp is due to a lesser extent to the evaporation of the filament material during operation, and to a greater extent to the inhomogeneities that arise in the filament. Uneven evaporation of the filament material leads to the appearance of thinned areas with increased electrical resistance, which in turn leads to even greater heating and evaporation of the material in such places. When one of these constrictions becomes so thin that the filament material at that point melts or completely evaporates, the current is interrupted and the lamp fails.

The majority of filament wear occurs when voltage is suddenly applied to the lamp, so its service life can be significantly increased by using various types of soft starters. A tungsten filament has a cold resistivity that is only 2 times higher than that of aluminum. When a lamp burns out, it often happens that the copper wires that connect the base contacts to the spiral holders burn out. Thus, a regular 60 W lamp consumes over 700 W when switched on, and a 100 W lamp consumes more than a kilowatt. As the coil warms up, its resistance increases, and the power drops to its nominal value.

To smooth out peak power, thermistors with a strongly decreasing resistance as they warm up, or reactive ballast in the form of capacitance or inductance can be used. The voltage on the lamp increases as the coil warms up and can be used to automatically bypass the ballast. Without turning off the ballast, the lamp can lose from 5 to 20% of power, which can also be beneficial for increasing the resource.

Halogen lamps

Halogen lamp

A new direction in the development of lamps is the so-called. IRC-halogen lamps (the abbreviation IRC stands for “infrared coating”). A special coating is applied to the bulbs of such lamps, which allows visible light to pass through, but retains infrared (thermal) radiation and reflects it back to the spiral. Due to this, heat loss is reduced and, as a result, the efficiency of the lamp increases. According to the company.

Although IRC halogen lamps do not achieve the efficiency of fluorescent lamps, their advantage is that they can be used as a direct replacement for conventional halogen lamps.

Special lamps

• Projection lamps - for slide and film projectors. They have increased brightness (and, accordingly, increased filament temperature and reduced service life); Usually the thread is placed so that the luminous area forms a rectangle.
• Double-filament lamps for car headlights. One thread for high beam, the other for low beam. In addition, such lamps contain a screen that, in low beam mode, cuts off rays that could blind oncoming drivers.

History of invention

Thomas Alva Edison

The incandescent lamp is the first electric lighting device that plays an important role in human life. It is this that allows people to go about their business regardless of the time of day.

Compared to other light sources, this device is characterized by simplicity of design. The luminous flux is emitted by a tungsten filament located inside a glass bulb, the cavity of which is filled with a deep vacuum. Later, to increase durability, instead of vacuum, special gases began to be pumped into the flask - this is how halogen lamps appeared. Tungsten is a heat-resistant material with a high melting point. This is very important, because in order for a person to see the glow, the thread must become very hot due to the current passing through it.

History of creation

Interestingly, the first lamps did not use tungsten, but a number of other materials, including paper, graphite and bamboo. Therefore, despite the fact that all the laurels for the invention and improvement of the incandescent lamp belong to Edison and Lodygin, it is wrong to attribute all the credit only to them.

We will not write about the failures of individual scientists, but we will give the main directions in which the efforts of the men of that time were made:

1. The search for the best filament material. It was necessary to find a material that was both resistant to fire and characterized by high resistance. The first thread was created from bamboo fibers, which were covered with a thin layer of graphite. Bamboo acted as an insulator, graphite as a conductive medium. Since the layer was small, the resistance increased significantly (as required). Everything would be fine, but the wood base of the coal led to rapid ignition.
2. Next, the researchers thought about how to create conditions of the strictest vacuum, because oxygen is an important element for the combustion process.
3. After this, it was necessary to create the connector and contact components of the electrical circuit. The task was complicated by the use of a layer of graphite, which is characterized by high resistance, so scientists had to use precious metals - platinum and silver. This increased the current conductivity, but the cost of the product was too high.
4. It is noteworthy that the Edison base thread is still used to this day - marked E27. The first methods of creating a contact involved soldering, but in this situation today it would be difficult to talk about quickly replaceable light bulbs. And with strong heating, such compounds would quickly disintegrate.

Nowadays, the popularity of such lamps is falling exponentially. In 2003, in Russia the amplitude of the supply voltage was increased by 5%; today this parameter is already 10%. This led to a reduction in the life of the incandescent lamp by 4 times. On the other hand, if you return the voltage to an equivalent value down, the luminous flux output will be significantly reduced - up to 40%.

Remember the training course - back in school, a physics teacher conducted experiments demonstrating how the glow of a lamp increases with increasing current supplied to the tungsten filament. The higher the current, the stronger the emission of radiation and the more heat.

Operating principle

The principle of operation of the lamp is based on the strong heating of the filament due to the electric current passing through it. In order for a solid material to begin to emit a red glow, its temperature must reach 570 degrees. Celsius. The radiation will be pleasant to the human eye only if this parameter is increased by 3–4 times.

Few materials are characterized by such refractoriness. Due to the affordable pricing policy, the choice was made in favor of tungsten, whose melting point is 3400 degrees. Celsius. To increase the area of ​​light emission, the tungsten filament is twisted into a spiral. During operation, it can heat up to 2800 degrees. Celsius. The color temperature of such radiation is 2000–3000 K, which gives a yellowish spectrum - incomparable with daylight, but at the same time not having a negative effect on the visual organs.

Once in the air, tungsten quickly oxidizes and breaks down. As mentioned above, instead of a vacuum, a glass flask can be filled with gases. We are talking about inert nitrogen, argon or krypton. This allowed not only to increase durability, but also to increase the glow strength. The service life is affected by the fact that gas pressure prevents the evaporation of the tungsten filament due to the high glow temperature.

Structure

A typical lamp consists of the following structural elements:

• flask;
• vacuum or inert gas pumped inside it;
• filament;
• electrodes - current terminals;
• hooks needed to hold the filament;
• leg;
• fuse;
• base, consisting of a housing, an insulator and a contact on the bottom.

In addition to standard versions made of conductor, glass vessel and leads, there are lamps for special purposes. Instead of a base, they use other holders or add an additional bulb.

The fuse is usually made of an alloy of ferrite and nickel and is placed in the gap on one of the current terminals. Often it is located in the leg. Its main purpose is to protect the flask from destruction in the event of a thread break. This is due to the fact that if it breaks, an electric arc is formed, leading to the melting of the remnants of the conductor, which fall on the glass bulb. Due to the high temperature, it may explode and cause a fire. However, for many years the low efficiency of fuses has been proven, so they are used less frequently.

Flask

The glass vessel is used to protect the filament from oxidation and destruction. The overall dimensions of the flask are selected depending on the deposition rate of the material from which the conductor is made.

Gas environment

If previously all incandescent lamps without exception were filled with vacuum, today this approach is used only for low-power light sources. More powerful devices are filled with inert gas. The molar mass of the gas affects the heat emitted by the filament.

Halogens are pumped into the bulb of halogen lamps. The substance with which the filament is coated begins to evaporate and interact with the halogens located inside the vessel. As a result of the reaction, compounds are formed that decompose again and the substance returns to the surface of the thread. Thanks to this, it became possible to increase the temperature of the conductor, increasing the efficiency and service life of the product. This approach also made it possible to make the flasks more compact. The design flaw is associated with the initially low resistance of the conductor when applying electric current.

Filament

The shape of the filament can be different - the choice in favor of one or the other depends on the specifics of the light bulb. They often use a thread with a round cross-section, twisted into a spiral, and much less often - tape conductors.

A modern incandescent lamp is powered by a filament made of tungsten or an osmium-tungsten alloy. Instead of conventional helices, bi-helices and tri-helices can be twisted, which is made possible by repeated twisting. The latter leads to a decrease in thermal radiation and an increase in efficiency.

Specifications

It is interesting to observe the relationship between light energy and lamp power. The changes are not linear - up to 75 W, the luminous efficiency increases, and if it is exceeded, it decreases.

One of the advantages of such light sources is uniform illumination, since light is emitted with equal strength in almost all directions.

Another advantage is associated with pulsating light, which at certain values ​​leads to significant eye fatigue. The normal value is considered to be a ripple coefficient not exceeding 10%. For incandescent lamps the parameter reaches a maximum of 4%. The worst indicator is for products with a power of 40 W.

Of all the electrical lighting available, incandescent bulbs run the hottest. Most of the current is converted into thermal energy, so the device is more like a heater than a light source. Luminous efficiency ranges from 5 to 15%. For this reason, the legislation contains certain rules prohibiting, for example, the use of incandescent lamps of more than 100 W.

Typically, a 60 W lamp is enough to illuminate one room, which is characterized by slight heating.

When considering the emission spectrum and comparing it with natural light, two important observations can be made: the luminous flux of such lamps contains less blue and more red light. However, the result is considered acceptable and does not lead to fatigue, as is the case with daylight sources.

Operating Parameters

When using incandescent lamps, it is important to consider the conditions of their use. They can be used indoors and outdoors at temperatures not less than –60 and not more than +50 degrees. Celsius. In this case, air humidity should not exceed 98% (+20 degrees Celsius). The devices can operate in the same circuit with dimmers designed to regulate light output by changing the light intensity. These are cheap products that can be replaced independently even by an unqualified person.

Kinds

There are several criteria for classifying incandescent lamps, which will be discussed below.

Depending on the lighting efficiency, incandescent lamps are classified (from worst to best):

• vacuum;
• argon or nitrogen-argon;
• krypton;
• xenon or halogen with an infrared reflector installed inside the lamp, which increases efficiency;
• with a coating designed to convert infrared radiation into the visible spectrum.

There are many more varieties of incandescent lamps related to their functional purpose and design features:

1. General purpose - in the 70s. of the last century they were called “normal lighting lamps”. The most common and numerous category is products used for general and decorative lighting. Since 2008, the production of such light sources has decreased significantly, which was due to the adoption of numerous laws.
2. Decorative purpose. The flasks of such products are made in the form of graceful figures. The most common types are candle-shaped glass vessels with a diameter of up to 35 mm and spherical ones (45 mm).
3. Local appointment. The design is identical to the first category, but they are powered by a reduced voltage - 12/24/36/48 V. They are usually used in portable lamps and devices that illuminate workbenches, machines, etc.
4. Illumination with painted bulbs. Often the power of products does not exceed 25 W, and for coloring the internal cavity is covered with a layer of inorganic pigment. It is much less common to find light sources whose outer part is painted with colored varnish. In this case, the pigment fades and crumbles very quickly.

1. Mirrored. The bulb is made in a special shape, which is covered with a reflective layer (for example, by spraying aluminum). These products are used to redistribute the light flux and increase lighting efficiency.
2. Signal. They are installed in lighting products intended to display any information. They are characterized by low power and are designed for long-term operation. Today they are practically useless due to the availability of LEDs.
3. Transport. Another broad category of lamps used in vehicles. Characterized by high strength and vibration resistance. They use special bases that guarantee strong fastening and the ability to quickly replace them in cramped conditions. Can be powered from 6 V.
4. Spotlights. High-power light sources up to 10 kW, characterized by high luminous efficiency. The spiral is laid compactly to ensure better focusing.
5. Lamps used in optical devices, for example, film projection or medical equipment.

Special lamps

There are also more specific types of incandescent lamps:

1. Switchboards - a subcategory of signal lamps used in switchboards and performing the functions of indicators. These are narrow, oblong and small-sized products with smooth parallel contacts. Due to this, they can be placed in buttons. Marked as “KM 6-50”. The first number indicates the voltage, the second indicates the amperage (mA).
2. Incandescent or photographic lamp. These products are used in photographic equipment for normalized forced mode. It is characterized by high luminous efficiency and color temperature, but a short service life. The power of Soviet lamps reached 500 W. In most cases, the flask is frosted. Today they are practically not used.
3. Projection. Used in slide projectors. High brightness.

The double-filament lamp comes in several varieties:

1. For cars. One thread is used for the low beam, the other for the high beam. If we consider lamps for rear lights, then the threads can be used for the brake light and side light, respectively. An additional screen can cut off rays that in the low beam lamp can blind oncoming drivers.
2. For airplanes. In a landing light, one filament can be used for low light, the other for high light, but requires external cooling and short operation.
3. For railway traffic lights. Two threads are necessary to increase reliability - if one burns out, the other will light up.

Let's continue to consider special incandescent lamps:

1. The headlight lamp is a complex design for moving objects. Used in automotive and aviation technology.
2. Low inertia. Contains a thin filament. It was used in optical-type sound recording systems and in some types of phototelegraphy. Nowadays it is rarely used, since there are more modern and improved light sources.
3. Heating. Used as a heat source in laser printers and copiers. The lamp has a cylindrical shape, is fixed in a rotating metal shaft, to which paper and toner are applied. The roller transfers heat, causing the toner to spread.

Efficiency

Electric current in incandescent lamps is converted not only into light visible to the eye. One part is used for radiation, the other is transformed into heat, and the third is converted into infrared light, which is not detected by the visual organs. If the conductor temperature is 3350 K, then the efficiency of the incandescent lamp will be 15%. A conventional 60 W lamp with a temperature of 2700 K is characterized by a minimum efficiency of 5%.

The efficiency is enhanced by the degree of heating of the conductor. But the higher the heating of the filament, the shorter the service life. For example, at a temperature of 2700 K, a light bulb will illuminate for 1000 hours, at 3400 K - several times less. If you increase the supply voltage by 20%, the glow will double. This is irrational, since the service life will be reduced by 95%.

Advantages and disadvantages

On the one hand, incandescent lamps are the most affordable light sources, on the other hand, they are characterized by a lot of disadvantages.

Advantages:

• low cost;
• there is no need to use additional devices;
• ease of use;
• comfortable color temperature;
• resistance to high humidity.

Flaws:

• fragility - 700–1000 hours if all rules and operating recommendations are followed;
• weak light output - efficiency from 5 to 15%;
• fragile glass flask;
• possibility of explosion if overheated;
• high fire danger;
• Voltage drops significantly shorten the service life.

How to increase service life

There are several reasons why the service life of these products may be reduced:

• voltage fluctuations;
• mechanical vibrations;
• high ambient temperature;
• broken connection in the wiring.

1. Select products that are suitable for the mains voltage range.
2. Carry out the movement strictly in the switched off state, since the slightest vibrations will cause the product to fail.
3. If the lamps continue to burn out in the same socket, then it needs to be replaced or repaired.
4. When operating on a landing, add a diode to the electrical circuit or connect two lamps of the same power in parallel.
5. You can add a device to the break in the power circuit for smooth switching on.

Technologies do not stand still, they are constantly developing, so today traditional incandescent lamps have been replaced by more economical and durable LED, fluorescent and energy-saving light sources. The main reasons for the production of incandescent lamps remain the presence of countries that are less developed from a technological point of view, as well as well-established production.

Today you can purchase such products in several cases - they fit well into the design of a house or apartment, or you like the soft and comfortable spectrum of their radiation. Technologically, these are long-outdated products.