There are three sections of copper wire with equal diameter, uniform thickness and length of a cm, B cm and C cm respectively. The resistance of a CM copper wire is 20 ohm and the length of a CM copper wire is 20 ohm The resistance of copper wire of C cm is 30 ohm. If three copper wires can form a triangle, try to find the value range of resistance of copper wire of B cm length (the resistance of copper wire is proportional to the length of copper wire)

There are three sections of copper wire with equal diameter, uniform thickness and length of a cm, B cm and C cm respectively. The resistance of a CM copper wire is 20 ohm and the length of a CM copper wire is 20 ohm The resistance of copper wire of C cm is 30 ohm. If three copper wires can form a triangle, try to find the value range of resistance of copper wire of B cm length (the resistance of copper wire is proportional to the length of copper wire)

The sum of the two sides of the triangle is greater than the third side, and the difference between the two sides is less than the third side. Therefore, the resistance range of copper wire with length of B cm is between (10,50) ohm

What kind of copper does the copper wire of cable belong to? Is it copper

The copper in the cable is electrolytic copper
Now, the technology of oxygen free copper rod continuous casting and rolling by up drawing method is widely used to produce bare copper wire
1 electrolytic copper (Cu) - continuous casting and rolling of oxygen free copper rod by up drawing method copper rod drawing annealing extruding insulation wire

For copper wire and iron wire of the same diameter, what percentage of the conductivity of iron wire is that of copper?

There are many factors affecting the image resistance. If only materials are considered, then it is OK to compare their resistivity ρ
ρ Fe 1.0 × 10-7 Ω M
ρ Cu 1.7 × 10-8 Ω M
So, 17%

I have 50 LED white diodes in series in the 220 V circuit, how much resistance do I need?

Generally do not use LED tubes in this way. If you have to use them in this way, the resistance in series is also related to the working current of the LED tube you are using. In the case of unknown working current of the LED tube, the value of the resistance cannot be determined