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# What is a 1/4 watt resistor? Answered

Alright, So I know the basics about resistors and what-not, but as I was buying beginner supplies, I noticed there were resistors in OHMs and Watts, What's the difference between the two? And like, can the unit Watt be transfered into OHMs? And which one would I use when my general area of working would be around basic LED work and noob stuff like that xD?

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The power rating of the resistor is stated in Watts. In other words, after you have designed your circuit, you look at the selected resistors, and you calculate the power dissipated (I) Power = current x voltage (P=IV, or P= V2 /R or P= I2 x R- you MUST select resistors with a power rating that exceeds the result.

So you don't work between Ohms and Watts, you work withBOTH in a successful, fire free, design.

Small error there: I = V/R *

Sir, I have made 14piece 3mm green led in series and the power supply is 220v and I connected single 10k ohm resistor with led so why resistor come burn

simply, it takes 9 volts down to 3 volts

one point i just want to add, to above explanation.generally LED drive current in the order of 2mA to 5mA.So we have to select a Resister based on this using KCL.

Steveastrouk is totally correct, but just to add a bit, the RESISTANCE of a resistor is how much it restricts a current flowing through it. So a 100 ohm resistor would give you a brighter LED than a 1000 (1K, or 1 kilohm) resistor. However, put too much current through and the LED would burn out. Current flowing through a resistor causes it to heat up. A large resistor will heat up less than a small one because of the larger surface area. The amount power a resistor can handle is given by it's WATT rating (see Steve's formula). If you're running single LEDs off low voltages, 1/4 or 1/8 watt resistors will be fine.

Look up ohms law for further reading. This is the formula you need to be familiar with when experimenting and designing circuits.