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    14.素養(4)
A -4A
B -1.6A
C 1.6A
D 4A

電感穩態相當於短路

總電阻 RT=3+(6//3) =5Ω

總電流 IT=12/5= 2.4A

𝑖L= 2.4 × 66+3= 1.6A

穩態時流過電感電流 𝑖L= 1.6A

開關打開瞬間,電感有維持電流恆定的功能,所以電流還是 1.6A


A τ = 1ms, 𝑖L = 2.4A
B τ = 1ms, 𝑖L = 1.2A
C τ = 2ms, 𝑖L = 2.4A
D τ = 2ms, 𝑖L = 1.2A

化戴維寧等效電阻

Rth = 6//6+2 = 5Ω

Eth = 12×66+6 = 6V

τ = 5m/5 = 1ms

t = 1秒 已經 穩態, 𝑖L = 6/5 = 1.2A


A 𝑖(t) = 50(1 - e -50t ) A
B 𝑖(t) = 50(1 - e -t/50 ) A
C 𝑖(t) = 5(1 - e -50t ) A
D 𝑖(t) = 5 e -50t A

電流源轉電壓源

電感穩態時電流 = 50 / 10 = 5 A

1𝜏 = 10 / 0.2 = 50

電感充電電流方程式 𝑖(t) = 5 ( 1 - e -50t ) A


A 𝑣(t) = 20(1 - e-100t ) V
B 𝑣(t) = 20(1 - e-50t ) V
C 𝑣(t) = 20 + 10 e-100t V
D 𝑣(t) = 20 + 10 e-50t V

先將電路如下圖的部份化成戴維寧等效電路

等效電阻 Rth = 2//6 = 1.5Ω

等效電壓 Eth = 40 × 62+6 = 30V

電感穩態時電流 = 30 / (1.5+3) = 203 A

1𝜏 = 4.5/90m = 50

電感充電電流方程式 𝑖(t) = 203 ( 1 - e -50t ) A

𝑣(t) = 203 ( 1 - e -50t ) ×3 = 20 ( 1 - e -50t ) A


A 10V
B 20V
C 40V
D 50V

電感穩態相當於短路,電路如下圖

總電阻=20+(10//10) = 25Ω

總電流 = 50/25 =2A

流過電感的電流剛好一半 = 1A (分流)

開關打開瞬間電流不變,如下圖

𝑣L = 50 - 20 -10 = 20V


A E1=10V、R1=2Ω、L1=100mH
B E1=10V、R1=4Ω、L1=20mH
C E1=20V、R1=2Ω、L1=100mH
D E1=40V、R1=4Ω、L1=50mH

電流10A,所以 E1=20V、R1=2Ω 或 E1=40V、R1=4Ω 符合

1τ = 20

RL = 20

R1=2Ω、L1=100mH 符合


A IL=20A、WL=20J
B IL=10A、WL=5J
C IL=20A、WL=20mJ
D IL=10A、WL=10mJ

電感穩態相當於短路

R2電阻被電感短路

電感電流 = 100 / 5 =20A

電感儲存能量 = 12 × 100m × 202 = 20J


A 流經電感器的初始電流值為1A且電路時間常數為80ms
B 流經電感器的初始電流值為0A且電路時間常數為80ms
C 流經電感器的初始電流值為1A且電路時間常數為0.2ms
D 流經電感器的初始電流值為0A且電路時間常數為0.2ms

電感充電瞬間電流不變,電流原本是 0 ,充電瞬間也是 0 A

τ = LR = 4m20 = 0.2mS