Is this ohms law/power equation calculation correct?

B

Bill S

New member
I have a +5V power supply and 4.7ohm resistor. Therefore, there is a 1.064A current (ohms law). Main question: wattage on the 4.7ohm resistor. Power equation: I^2*R. So, power = 5.319W. Would by resistor need to be rated for somewhere over this value?
 
If it were me I would be using 7 OR 10 watt resister...wire wound ....carbon or composite may deteriorate over time...
 
Your calculations are correct. Ratings as a general rule, should always be twice what you will be using. You'd use a 10W resistor. You can't get normal carbon film resistors beyond 2 watts without ordering them special. You'd get a 10 watt wirewound resistor. Are you sure its not a 4.7 kilo-ohm resistor?
 
Yes, your conclusions are correct. Pick a resistor with a power rating slightly greater than your calculated power.
 
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