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    I have this question that's got me completely stumped..
    Resistors have different power ratings. The most commonly used carbon film resistors have a power rating of 0.25W. calculate the maximum current allowable for a 4.7 ohm resistor.

    I have worked it out like this but i know its wrong! :
    I = 0.25 / 4.7 = 0.05319 x 0.05319

    thanks for the help guys x
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    (Original post by smellybelly1991)
    I have this question that's got me completely stumped..
    Resistors have different power ratings. The most commonly used carbon film resistors have a power rating of 0.25W. calculate the maximum current allowable for a 4.7 ohm resistor.

    I have worked it out like this but i know its wrong! :
    I = 0.25 / 4.7 = 0.05319 x 0.05319

    thanks for the help guys x
    P=I2 R

    I2=P/R

    I=sqrt(P/R)
    =sqrt(0.25/4.7)
    =sqrt(0.0532) *3sf is enough... those resistors are probably 5% tolerance anyway
    =0.231
 
 
 
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