A resistor is an element of an electrical circuit. Unlike transistors and diodes, a resistor is a passive element. An ideal resistor characterizes only the resistance to electric current, but since in the material world there is no ideal, then in reality the resistor has a nonlinear I - V characteristic and parasitic capacitance and inductance. In general, an ordinary resistor is a frame with a high-resistance wire wound around it, but there are also variable resistors (with variable resistance).
pencil, wire, paper clip, ceramic cylinder, nichrome
Make the simplest variable resistor. Take a simple pencil and carefully cut it in half lengthwise. Do not damage the graphite lead.
On one end of the half of the pencil, in which the lead remains, wind several turns of wire. Wind the wire so that it is in contact with the lead.
Next, take a paper clip and slide it over the pencil. The wire will be the fixed contact, and the paper clip will be the movable one. As you move the paper clip along the pencil, the resistance of the homemade resistor will change.
Make a permanent resistor. Take a ceramic cylinder and wind nichrome wire around it. Before doing this, calculate the thickness and length of the wire.
Let's say the resistor should be 100 tons, and the voltage should be 50 V. Use the formula: I = P / U, where I is the current, P is the power, U is the voltage. Next, plug in the values. You will get: I = 100/50 = 2 amperes.
In the handbook, see what section of nichrome wire will withstand such a current. Then, winding the resistor with the desired wire, measure the resistance. As you wind up to the resistance of the required value, fix the wire leads and that's it, the resistor is ready.