电路chapter5(下).pptVIP

homework P196 5.32 P202 5.61 P204 5.70 Using the three-factor method 2. + - R1 1.2A U 6? R2 3? 4? R3 t=0+ + - t=0 12V + - R1 L S 1H U 6? R2 3? 4? R3 + - 2 1.2 O Plot Plot 4 2.4 0 + - R1 i L U 6? R2 3? 4? R3 t= ? + - the switch has been closed for a long time. It is opened at t=0, find uC、vB and vA at t ?0 . 【Solution】(1) t≥0 , uB Example Hence   ? ? Attention :  (2) vB (3) vA ? ? ? ? Example The switch has been in position 1 for a long time. At time t=0, switch is moved to position 2. find uC(t) . 2A 4? 1? 0.1F + uC － + － 4? i1 2i1 8V + － 1 2 Solution 4? + － 4? i1 2i1 u + － 2A 4? 1? 0.1F + uC － + － 4? i1 2i1 8V + － 1 2 Example k2(t=0.2s) i 10V 1H k1(t=0) 3? 2? The switch k1, k2 has been opened for a long time. At t=0, the switch k1 is closed. At t=0.2s, the switch k2 is closed. Find i(t). 0 t 0.2s Solution t 0.2s i 10V 1H k1(t=0) 3? 2? k2(t=0.2s) (0 t ? 0.2s) ( t ? 0.2s) i t(s) 0.2 5 (A) 1.26 2 Find , , and Example ,the switch is closed at t=0. Solution: According to the charge conservation: Hence Example Find , and Solution According to the flux conservation: hence Example the analysis of pulse sequence 1 .The response under a single pulse R C us uR uc i 1 0 T t us (1) 0tT (2) t T uc(t ) uR(t ) t 0 t 0 (a) ?T, uR is the output uR The output is nearly the differentiation of the input signal. (b) ? T, uc is the output t 0 The output is nearly the integration of the input signal. R C us uR uc i uC T T 2. Pulse sequence t 0 (a) ?T uR uc R C us uR uc i t 0 (b) ? T U1 U2 uc uR R C us uR uc i Exercise t=0- The switch has been opened for a long time. It is closed at t=0, find uC, iC and i1 at t ≧0. Solution + - S t=0 6V 1? 2? 3? + - t=0- 1? 2? + - 6V 3? + - + - S t=0 6V 1? 2? 3? + - 2? 3? + - + - S t=0 6V 1? 2? 3? + - 0.1H 150 60V S 100 20 100 Exercise The switch is closed at t=0, find i. Solution 150 6