The relationship between resistance and temperature?

The relationship between resistance and temperature?

Temperature has different effects on the resistance of different substances
Conductor
At a temperature close to room temperature, the resistance of a good conductor is usually proportional to the temperature
R＝R0＋aT
A in the above formula is called the temperature coefficient of resistance
semiconductor
The resistance of undoped semiconductors decreases with temperature
R＝R0×e^(a/T)
When the temperature rises from absolute zero, the resistance of semiconductors first decreases. When most of the charged particles (electrons or holes) leave their carriers, the resistance will increase slightly with the temperature due to the decrease of the activity of charged particles. When the temperature rises higher, new carriers (like undoped semiconductors) will be produced in semiconductors, The importance of the original carrier (due to impurity) decreases, so the resistance decreases again

Relationship between resistance and temperature (online, etc.)
It's metal
Does it mean that high temperature leads to high resistance
Low temperature, low resistance?

No matter how low the temperature is, the resistance of ordinary filament (tungsten filament) can not be zero, because the material of ordinary filament itself is not superconducting. However, when the temperature is reduced, the resistance value is correspondingly smaller, because the lower the temperature is, the less intense the molecular motion is, Only superconductor will suddenly drop to zero when the temperature drops to its critical value. Other common materials generally decrease resistance with the increase of temperature, but also increase resistance with the increase of temperature

A construction site needs to install a 220v1000w bulb. 500m away from the power supply, a single core aluminum conductor with a resistance of 0.016 ohm per 10m is used as the transmission line
The power is? W
Lamp power

The wire is a double wire, so it should be 500 * 2 = 1000 meters, the resistance of the wire is 1000 / 10 * 0.016 = 1.6 Ω, the resistance of the bulb is, the square of the voltage divided by the power, that is: 220 * 220 / 1000 = 48.4 Ω, the total resistance of the line: 1.6 + 48.4 = 50 Ω, the total current: 220 / 50 = 4.4 a, at this time, the actual power of the bulb is, the square of the current

Average ohmic resistance per meter per phase of aluminum bar
Aluminum 5.25 * 230 * 2, aluminum 5 * 200, aluminum 5 * 100

Is the first aluminum bar? The resistivity of aluminum is about P = 2.8 X10 ^ - 8 Ω M. therefore, if we assume that the cross section of aluminum bar is s and the length is l, then the resistance of this section of aluminum bar is r = PXL / s. This is a very simple formula. Just substitute the above data, and pay attention to the unit change. For 1-meter-long aluminum bar, 5 * 200, s =