Question

Consider the electric circuit shown in Fig. Determine : (i) the value of R so that load of 20 ohm should draw the maximum power, (ii) the value of the maximum power drawn by the load.

Answer 1

Maximum power transfer takes place when load resistance 

= Thevenin’s Resistance = 20 ohms, here 

R/60 = 20 ohms, giving R = 30 ohms 

V_TH = 180 × (60/90) = 120 volts 

Current through load = 120/40 = 3 amps 

Maximum Power Load = 180 watts