ABSTRACT
Thus,with a variable purely resistive load, themaximum power is delivered to the load if the load resistance R is made equal to the magnitude of the source impedance.
Condition 2. Let both the load and the source impedance be purely resistive (i.e. let x=X=0). From equation (1) it may be seen that the maximum power is transferredwhenR=r (this is, in fact, the d.c. condition explained in Chapter 15, page 239)
Condition 3. Let the load Z have both variable resistance R and variable reactanceX. From Figure 38.1,
current I = E (r +R)+ j (x +X) and
|I | = E√ [(r +R)2 + (x + x)2]
The active power P delivered to the load is given by P =|I |2R (since power can only be dissipated in a resistance) i.e.
