(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

Please see my attachment. From the circuit

Energy transferred to the load E = Ir + IR, where r is the internal resistance and R is Load Resistance. so

I = E/(r+R)

2. Relevant equations

3. The attempt at a solution

The Power W is W = I^{2}R = E^{2}R/(r+R)^{2}

Upto this i understand. I can't understand the following steps

As R changes, so does W. W will be maximum when dW/dR is zero

that is d/dR(E^{2}R/(r+R)^{2}) = 0

My question is why W is maximum when dW/dR = 0. Why dW/dR concept is introduced here

1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

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# Homework Help: Maximum power theory in electronics

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