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# Resistors- Electronics Crash Course #9

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The most basic electronics component- the ressistor. We will learn how they are made, how they work, how to use them in equations and how to use them in circuits.

The resistor is very simple in nature. As it’s name suggests, its job is to resist the flow of electricity. More specifically, they limit the flow of electrons.

Lets think of electricity as water. Rresistors are like a clogged water pipe, slowing down the flow of water.

Resistors are made by wrapping a partially conductive strip around a thick insulating piece. There are 3 types of resistors: carbon, metal, or metal-oxide film. with metal and metal oxide film resistors being the commonly used resistors. We also have variable resistors such as potentiometers that change resistance by physically moving the electrical contact along a resistive track- shortening or lengthening it.

The unit for ressistance is ohms and the symbol of a ressistor when used in a schematic is this.

Ressistors are color coded using 4-6 bands of colours to denote their resistance as in how ressistive they are. You can use an online calculator or a chart like this to decode the colours.

Lets now talk about the uses of resistors.

We can reduce current in our circuit using a resistor. To calculate the value of ressistor we need. We can use Ohms law. Do note that wiring a resistor in series will add the sum of of the resistor while wiring them in parallel will result in a resistance less than that of an individual resistor.

We can also use resistors as voltage dividers. By wiring 2 resistor in series, we can induce a voltage drop at the middle point of our resistor. We can calculate this voltage drop using Ohm’s law.

When we attach digital sensors to microcontollers like arduino or raspberry pi, we can reduce the noise of these sensors by attaching a pull up or pull down resistor in a cirucit like this. These circuits usually use high resistance resistors like 10k ohm resistors to feed a small current to override digital noise.

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