The tungsten filament of an incandescent light bulb is

When heated, the tungsten filament of an incandescent light bulb reaches a temperature of 2300 °C. If the diameter of the filament is 20 µm and its length is 0.5 m, then what will be the current density I and the current j flowing through it at a voltage of 200 V? The resistivity of tungsten at 0 °C is 5.510^-8 Omm, and the temperature coefficient of resistance is 4.6*10^-3 K^-1.

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The tungsten filament of an incandescent light bulb has a diameter of 20 microns and a length of 0.5 m. At a voltage of 200 V, a current strength I flows through the filament, which we must find. To do this, we use Ohm's law: U = R * I, where U is the voltage on the thread, R is the resistance of the thread, I is the current strength.

The resistance of the thread can be found using the formula: R = ρ * L / S, where ρ is the resistivity of the thread material, L is the length of the thread, S is the cross-sectional area of ​​the thread. The cross-sectional area of ​​the thread can be found using the formula: S = π * d^2 / 4, where d is the diameter of the thread.

Thus, the current strength I is equal to: I = U / R = U * S / (ρ * L * π * d^2 / 4).

Substituting known values, we get:

S = π * (20*10^-6)^2 / 4 = 3.14 * 10^-13 m^2

R = ρ * L / S = 5.5 * 10^-8 * (1 + 4.6 * 10^-3 * (2300 - 0)) * 0.5 / 3.14 * 10^-13 = 3.5 Ом

I = U / R = 200 / 3.5 = 57.14 А

Thus, the current density j flowing through the filament is 114.29 A/m^2 (since S = π * (20*10^-6)^2 / 4 = 3.14 * 10^-13 m^2).

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The tungsten filament of an incandescent light bulb has a very high temperature when incandescent - 2300 °C. To calculate the current density and current flowing through the filament, it is necessary to use the following data: filament diameter - 20 µm, filament length - 0.5 m, filament voltage - 200 V. The resistivity of tungsten at 0 °C is 5.510^-8 Omm, and the temperature coefficient of resistance is 4.6*10^-3 K^-1.

To calculate the current density, you must use Ohm's law:

I = U / R,

where I is the current, U is the voltage on the filament, and R is the resistance of the filament.

The resistance of the thread can be found using the formula:

R = ρ * L / S,

where ρ is the resistivity of the filament material, L is the length of the filament, and S is the cross-sectional area of ​​the filament.

The cross-sectional area of ​​the thread can be found using the formula for the area of ​​a circle:

S = π * d^2 / 4,

where d - thread diameter.

Thus, we can find the resistance of the thread and, using Ohm's law, find the strength of the current flowing through the thread. We can then find the current density by dividing the current by the cross-sectional area of ​​the filament.

Let's calculate all the necessary parameters:

S = π * d^2 / 4 = 3.14 * (20 * 10^-6)^2 / 4 = 3.14 * 4 * 10^-12 = 1.26 * 10^-11 m^2

R = ρ * L / S = 5.5 * 10^-8 * 0.5 / 1.26 * 10^-11 = 2.19 Ом

I = U / R = 200 / 2.19 = 91.32 А

j = I / S = 91.32 / 1.26 * 10^-11 = 7.25 * 10^12 A/m^2.

Thus, the current density is 7.25 * 10^12 A/m^2, and the current strength is 91.32 A.

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1. Tungsten filament is a reliable and durable material for light bulbs.
2. The brightness of the light from a tungsten filament bulb is very pleasing to the eye.
3. Tungsten filament light bulbs have high efficiency and low energy consumption.
4. The tungsten filament does not oxidize at high temperatures, which ensures a long service life of the light bulb.
5. Tungsten filament has high heat resistance, which allows the use of light bulbs with such a filament in various conditions.
6. Bulbs with tungsten filament have stable light brightness throughout their entire service life.
7. Tungsten filament provides excellent color rendering, which is especially important for lighting for interior purposes.

Peculiarities:

The tungsten filament provides high brightness, making incandescent bulbs ideal for home lighting.

Tungsten filament light bulbs have a long lifespan, saving you time and money on replacing them.

Tungsten filament has high thermal resistance, which allows light bulbs with it to work at high temperatures without damage.

Tungsten filament light bulbs provide stability and reliability, which is especially important for industrial and commercial purposes.

Tungsten filament is an environmentally friendly material that does not contain harmful substances, which makes light bulbs with it safe for home use.

Incandescent bulbs with tungsten filament are highly efficient, which saves energy.

Tungsten filament is a high quality material, which guarantees the durability and reliability of light bulbs with it.