# Which resistor do I use?

Hello everyone! I am looking for a 10kOhm resistor so I can control my Arduino Uno with a button. There are 10kOhm resistors that are 1/4 watt, 1/2 watt, 1 watt, and so on. What's the difference and which one should I choose?

I need help ASAP!

Either is fine. W = E * I

From the above equation

W = E x E/R

So the power in the R is

W = 5 x 5 / 10k. watts.

A 1/4 watt is all you need but any larger size will also work.

Weedpharma

Why use a resistor, when you can use Arduino's internal pullup resistors. Use INPUT_PULLUP in your code. Leo..

To answer part of your question, the difference is in how much power it can safely dissipate in heat. A large object has more surface area to transfer heat to the surrounding air, and a greater thermal mass so it takes longer to heat up. So large wattage resistors are necessarily larger (except for water cooled ones).

A resistor is one of the few devices in the universe that is 100% efficient, as all of the electrical energy supplied to it is converted to heat!

Thanks guys so much for your support! I will buy 1/4 watt 10kOhm resistors!

A resistor is one of the few devices in the universe that is 100% efficient, as all of the electrical energy supplied to it is converted to heat!

Or... 100% inefficient! :D Assuming you are not trying to build a heater, I'd say all of the energy dissipated by a resistor is wasted.

If your goal is to generate heat, a lot of things are 100% efficient. A light bulb generates light & heat and when the light hits an object and gets absorbed, the light is converted to heat. A speaker generates sound & heat and when the sound hits an object and is absorbed the sound is converted to heat.

In the winter when you are heating your house, none if this energy is wasted, since it means you don't have to use as much fuel heating your house. (But electrical heating is usually not the most economical.) If you are running an air conditioner in the summer all of that heat energy is wasted, plus it takes more energy from the air conditioner to remove that extra heat.

DVDdoug: If you are running an air conditioner in the summer all of that heat energy is wasted, plus it takes more energy from the air conditioner to remove that extra heat.

What if the resistor is in a control circuit that makes the air conditioner function more efficiently?

DVDdoug: A light bulb generates light & heat and when the light hits an object and gets absorbed, the light is converted to heat.

Not necessarily. It could be changing the energy in some chemical bonds such as when exposing a photoresist.

Russell (in pedantic mode this morning :-) )

Pedants of the world unite!!

Weedpharma

weedpharma: Pedants of the world unite!! Weedpharma

...You have nothing to lose but the series of oval shaped steel loops that interlock at successive right angles around parts of your body that permit you mobility (requiring a locking device at each end to allow attachment and removal), thus rendering you captive.

Well, actually it's likely that they have something to lose, for example their wallet or theater tickets.