How to calculate power

Forum 2005-2010 (read only) General Frequently-Asked Questions
1

So im reading "introductory electroncis for scientists and engineers" by "robert e simpson".

I just want confirmation on something he says:

You have two resistors, in this case two 1k Ohm resistors that are rated at 1/2 W.

In series the total resistance is obviously 2k Ohms, and he says the total power is 1 W.

In parallel the total resistance is obviously 500 Ohms, and he says the total power is 1W.

My question is can you really simply add the power together? ie: 1/2 + 1/2 = 1 W.

Instead of a 200 Ohm resistor rated at 1 W, i can use two 100 Ohm resistors in series rated at 1/2 W? I just found this to be too easy to be true.

2

In both configurations the power divides by two.

In series the current through both resistors is the same but the voltage across each resistor is half of the total. In parallel the same voltage is across each resistor but the current through each resistor is half of the total. For calculating the power dividing the voltage by two has the same effect as dividing the current by two.

It is both easy and true :wink:

(* jcl *)

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