如圖所示，調整 使 有最大的功率。問 獲得的功率？
A正確答案
B
C
D
答案與詳解
為什麼答案是 A
正確答案。求戴維寧等效：移除RL，電流源開路→Rth = R + R/2 + R/2 = 2R；開路電壓Vth = I×R（電流I全部流過並聯電阻R，上下R/2無電流）；最大功率Pmax = Vth²/(4Rth) = (IR)²/(4×2R) = I²R²/8R = I²R/8
考點：最大功率轉移定理考點：戴維寧等效電阻考點：開路電壓計算
載入中…
正確答案。求戴維寧等效：移除RL，電流源開路→Rth = R + R/2 + R/2 = 2R；開路電壓Vth = I×R（電流I全部流過並聯電阻R，上下R/2無電流）；最大功率Pmax = Vth²/(4Rth) = (IR)²/(4×2R) = I²R²/8R = I²R/8
