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hi, how should i go about solving this question?
Oh?When Rx = 18 ohms, the maximum power is obtained.
How many watts is dissipated in Rx when Rx = 18R ??????
The circuit is very complex until you realise one thing.
Firstly, remove the 6R, 18v and 12R.
Maximum power in Rx is achieved when Rx is equal to 3R.
To see if this is true, simply change Rx to 2R or 4R and work out the watts dissipated.
Another way to look at it is this: When Rx is zero, the watts dissipated is zero, when Rx is very high, the watts dissipated is very small.
Make Rx = 3R and see what happens:
The voltage across Rx will be 18v.
Now put-back the 6R, 18v supply and 12R load resistor.
The voltage across Rx is 18v. This means no current will flow though the 6R resistor because it has 18v on each end.
Current through Rx = 36v/6R = 6 amp
Wattage dissipated by 3R = V2/3 = 108watts or I2xR = 62 x 3 = 108watts
We have turned a seemingly complex question into a very simple answer.
See this review on Spot The Mistake:
**broken link removed** .
Current via 36v supply through 3R and 2R = 36/5 = 7.2A
Current delivered by 18v supply 18 - 14.4v through 6R = 3.6/6 = 0.6A
This concept is entirely wrong. I don't know how you come to this reasoning. The 3R has 36v in series with it.Again you fail to take into account that 3R is in parallel with Rx. The voltage across Rx from the 18 volt source is 3 volts.
Unless otherwise stated, supply voltages are fixed DC voltages capable of supplying the current required to solve the problem.whether the sources are to be regarded as constant current or constant voltage.
I suggest you go and set up the circuit and see what happens.
You are trying to turn a simple circuit into something very complex.
Take one part of the circuit at a time.
Don't try adding in the 6R because it has 18v in series with it.
This concept is entirely wrong. I don't know how you come to this reasoning. The 3R has 36v in series with it.
All this dense maths is a bit beyond me, but I think the problem is a bit obtuse
it states units are in V,A,Ω but it's not clear whether the sources are to be regarded as constant current or constant voltage.
Firstly you say Rx must be 18R
The you say the dissipation is 10368 watts.
Now you say Rx is 2R and the dissipation is 112Watts.
How many more guesses are you going to provide???????????
A voltage-source has zero impedance when it is a voltage source. You cannot say the 6R is in series with the 2R when it has a voltage in series with it - and not account for the voltage.
LTSpice simulation of the problem shows [as you have already clearly proved] that the Wpeak occurs when the resistance is 18R.