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Equivalent Circuits Resistor Power
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petersanch:
Basic EE question. I have a circuit with 4 batteries in series and I need series resistance of 12 ohm to limit current to 0.5 A.
The current in the top and bottom circuits is the same but the power ratings of the resistors should be different?
P=6^2/12 =3watt for the bottom resistor
P=1.5^2/3 =3/4watt for the top resistors

Is there any reason to use one circuit over the other?

Cheers
IanB:

--- Quote from: petersanch on January 06, 2019, 03:33:02 am ---Basic EE question. I have a circuit with 4 batteries in series and I need series resistance of 12 ohm to limit current to 0.5 A.
The current in the top and bottom circuits is the same but the power ratings of the resistors should be different?
P=6^2/12 =3watt for the bottom resistor
P=1.5^2/3 =3/4watt for the top resistors

Is there any reason to use one circuit over the other?

Cheers

--- End quote ---

Your top circuit is more robust. But there is no reason to distribute the resistors like that. You could group them all together in the same position as R5 in the bottom circuit. After all, putting four 3 ohm resistors in series makes a 12 ohm resistor. The circuit is more robust because the 3 ohm resistors are less stressed, and the heat dissipation is spread out over a larger surface. If one 3 ohm resistor fails you still have the other resistors there for protection.
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