So I ordered 30 resistors of different values on-line. I didn't really know they came in different sizes so I ordered 1w ones. Now they are big, on the breadboard they can only fit two spaces apart, but that's not the problem. I was only wondering whether the fact that they're 1w makes any difference with basic Arduino projects?
They'll be fine. The standard ones are 1/4 watt so yours are able to deal with more power than your Arduino can produce is all.
It makes no difference, the resistor value (how many ohms) makes a circuit work.
For Arduino circuits you would need resistors of 100 ohm to 1 Mega ohm. Resistors of 1W are mostly up to a few kilo Ohm, so I doubt if you have a good set of different resistor values.
There are boxes with metal-film resistors with all kind of values. They are not expensive.
Suppose you have a led of 20mA connected to a Arduino pin.
Assume it is a red led with a voltage drop of 1.5V.
The resistor you would need is (5V - 1.5V) / 20mA = 175 ohm.
Lets use a resistor of 180 ohm.
The power consumed by the resistor is 3.5V /180 ohm * 3.5V = 68mW.
The resistor would heat up with 68 milli Watt.
So a resistor of 100mW would be okay.
Using a resistor of 1W doesn't make a difference, but it also makes no sense to use such a big resistor.
Ah, thanks for the explanation. 