What size resistor to choose?

[AndreeU17]

Its very basic question i know, however, i was curious as to what size resistor would we need for specific schematic. I'm not sure how to test whether i need a resitor around 100 Ohms or 1M Ohms. How do i test what resistor i need? I know i need to know the voltage that will be running thru the circuit but how can i check to see if i need a big resistor or small value resistor.

 

[Harald Kapp]

R=V/I
If you know the voltage V and the current I, you calculate R. Or calculate V or I if you know the 2 other parameters.

For more in-detail help we need to see the schematic of the respective part of your circuit and a short explanation what this part of the circuit is expected to do.

 

[Anon_LG]

It depends on the power rating of the component, this will be in watts if you want a more detailed explanation on how resistance affects the current see here. Post the schematic and what you want it to do.

 

[(*steve*)]

When I think of "size" for a resistor, I think of power rating. The value in ohms is, well, the value of the resistor.

In general you don't "know" what value is required, you calculate it. Harald is 100% correct in saying that we need to see the circuit because there are many different calculations depending on exactly what the resistor has to do.