Electronics questions (power handling of resistors in series and parallel)

Feek

Feek

Feek

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Looks like a school question, trust me, it's not!

Total resistance is very easy to work out, the total power handling capability is not quite so clear.

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200W as each branch can only handle 100W, any more and the first resistor blows up.
 
Current equal through both rows of resistors. Calculated I for 10R based on max power of 100, which gives 20W dissipated by each 50R. So total power that can be dissipated is 5x100W + 3 x20 ???
 
So both branches are 100ohms, so they take 50/50 current split.

The highest ohm resistor (that is the one that has the biggest power for a given current) is 50 ohms for either branch

So the highest current a single branch can take is sqrt(100/50) so 1.41amps

Given its an equal resistance split and therefore an equal current split in both branches the total current is doubled, so 2.828 amps

Total resistance is 50ohms, so a current of 2.828amps going across 50ohms gives a total power dissipation of 400w

*Disclaimer, not an electrical engineer
 
firstborn said:
It's each component that can handle 100W not each branch surely.
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I might have misread the question, I read power handing of the circuit to mean what is the maximum power the circuit could be driven at. As the resistance of each branch of the circuit is the same then the current will be the same, so if say you drove 300w into the circuit then 150W would go down each branch and blow up the first resistors as they can only handle 100W. That was what I meant.
 
adolf hamster said:
So both branches are 100ohms, so they take 50/50 current split.

The highest ohm resistor (that is the one that has the biggest power for a given current) is 50 ohms for either branch

So the highest current a single branch can take is sqrt(100/50) so 1.41amps

Given its an equal resistance split and therefore an equal current split in both branches the total current is doubled, so 2.828 amps

Total resistance is 50ohms, so a current of 2.828amps going across 50ohms gives a total power dissipation of 400w

*Disclaimer, not an electrical engineer
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Had some numbers switched around in my head - my first attempt was incorrect!
 
Bear said:
I might have misread the question, I read power handing of the circuit to mean what is the maximum power the circuit could be driven at. As the resistance of each branch of the circuit is the same then the current will be the same, so if say you drove 300w into the circuit then 150W would go down each branch and blow up the first resistors as they can only handle 100W. That was what I meant.
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Each resistor in the network will only see a percentage of the voltage across it though ? so if you had say 4 identical 100w resistors in series with a load of 25 amps and a voltage of 12v then each resistor would have to handle 75watt of power right? or I might be talking complete rubbish.
 
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Rroff said:
Each resistor in the network will only see a percentage of the voltage across it though ? so if you had say 4 identical 100w resistors in series with a load of 25 amps and a voltage of 12v then each resistor would have to handle 75watt of power right? or I might be talking complete rubbish.
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Hence I stated my interpretation of the question as being the circuit being driven by 200W. If you drove the input of that circuit with 200W from an amplifier, the power handling of that circuit will be limited by the first resistor, hence 100W on each branch. Others interpreted the question to mean the maximum dissipation of the circuit, which was why I think I misread the question as the two are not the same thing.
 
I'm no electrical engineer so this is as much for my education - but 200 watt from a power amp is still made up of volts/amps (though ac in the case of audio) so I'd assume same rules apply? R1 would only see 5% of the voltage across it and R7 25%?
 
The current in each branch is always equal since the total resistance in each branch is equal.

For any given current, the power dissipation in the 50 Ohm resistors will be highest since P=(I^2)*R. Therefore the 50 Ohm resistors are the limiting components in terms of circuit power dissipation.

The 50 Ohm resistors will reach their power limits at a branch current of sqrt(P/R)=1.414A.

The total circuit dissipation in this case is (I^2)*R for each branch (1.414^2)*100*2 = 400W.

/edit: Adolf Hamster got it. Lots of people giving wrong answer (guesses?!) before that...

/edit2: "Total Power handling of this circuit" is bizarre wording. It would be better defined as "maximum power dissipation capability". You would be better off talking about current or voltage handling ability.
 
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p4radox said:
/edit2: "Total Power handling of this circuit" is bizarre wording. It would be better defined as "maximum power dissipation capability". You would be better off talking about current or voltage handling ability.
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Yeah watts is useful sometimes but its far better (or at least I find it easier) to be working with volts and amps and figure the rest out if needed.
 
When working with radio transmitters (this is a dummy load), I always work in Watts. Hence the reason for the question.
 
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