1/4 watt or 1/2 watt resistor
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1/4 watt or 1/2 watt resistor

 
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728 juicer



Joined: 22 Dec 2006
Posts: 1
Posted: Fri Dec 22, 2006 4:01 pm    Post subject: 1/4 watt or 1/2 watt resistor Reply with quote
I plan on replaceing a resistor in a circuit board. The mod is to up voltage from 100v to 135-140v. The resistor needs to be 75K ohm. From my math, it looks like it needs a 1/4 watt. Would there be any problems running either a 1/4 or a 1/2 watt resistor? Here is my math..
135v = I*75,000. SOlve for I (amperage)
135 / 75000 = I
I= .0018 amps
Now, Wattage = I*E
135v * .0018 = .24 watts, or, right at 1/4 watt.

Here is the part number for the resistors I have coming from Digikey..
75.0KXBK-ND MFR-25FBF-75K0 RES 75.0K OHM 1/4W 1% METAL FILM Yageo Corporation 75.0K 0.25 W (1/4 W) ±1% Axial

Thanks for your help all as I am kinda new at electronics..

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neon



Joined: 25 Feb 2006
Posts: 570
Posted: Fri Dec 22, 2006 7:13 pm    Post subject: Reply with quote
well you forget the enviroment it may dissipate 1/4w and a 1/4 w should be ok but in the longer run how much heat would it be subjected to and stress a 1/2 w is more desirable or even higher if in a hot spot.
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