# power (W) sum of series & parallel circuit.

1. ## power (W) sum of series & parallel circuit.

i will design series circuit with resist.
each of 10 resist consist of series circuit.

i know power sum of parallel circuit

but what is the allowable power of each of resist.
and i don't know mathmatic formula  •

2. ## Re: power (W) sum of series & parallel circuit.

In both series and parallel combinations, you can add the individual power dissipated by individual components to get the total. •

3. ## Re: power (W) sum of series & parallel circuit.

how to calculate mathmedical formula of power sum? •

4. ## Re: power (W) sum of series & parallel circuit.

You have calculated correctly the power dissipated by each resistor in each case.

However, in engineering you have to leave a safety margin when selecting components. Ideally, the higher the safety margin the better, but practically, there is a cost (and size) implication so you have to strike a balance between the two. After calculating the power dissipation (say P) like you did, different folks use different safety factors to obtain the minimum power rating for the resistor. There are factors like 1.25*P; 1.3333*P; 1.5*P and so on. Here, 1.25*P gives the least safety margin and 1.5*P gives the most. I go for 1.5*P. 5. ## Re: power (W) sum of series & parallel circuit.

Hi,

i will design series circuit with resist. 