VIEWS: 1 PAGES: 5 CATEGORY: Physics POSTED ON: 10/17/2011 Public Domain
PHY301 – Circuit Theory Virtual University PHY 301 LECTURE 16 Example: Calculate the voltage Vac . Solution: We want to calculate the voltage Vac. To solve this problem the circuit can be redrawn as Let the current I is flowing through the circuit. The KVL equation will be 1 10kI + 20kI + 30KI -6 = 0 1 1 1 10kI + 20kI + 30KI = 6 1 1 1 60kI = 6 1 I = 6/60k 1 I = 0.1mA 1 Now Vac will be equal to Vac = (10k + 20k)I 1 = 30k(0.1mA) Vac = 3 Volts Example: Calculate the voltage Vac . Virtual University of Pakistan Page 67 PHY301 – Circuit Theory Solution: We want to calculate the voltage V .First we will have to calculate the voltage across 40k resistor. bd Let the current I be flowing through the loop. 1 Applying KVL 10kI + 9 + 40kI + 10kI – 6 = 0 1 1 1 60kI = -3 1 I = - 3/60k 1 = - 0.05 mA So, voltage across 40k resistor V = (-0.05m)(40k) 40k = - 2 volts ---------- (A) We want to want to calculate Vbd we will redraw the circuit as Now to calculate V we take the path bdcb bd Applying KVL V -V -9 =0 bd 40k by putting the value of V from equation (A) we have 40k V – (–2) –- 9 =0 bd V +2 –- 9 =0 bd V = 7 Volts bd Example: Calculate the current I . 0 Solution: We want to calculate the current I . The circuit can be redrawn as 0 Virtual University of Pakistan Page 68 PHY301 – Circuit Theory KVL for mesh 1 Here I = 120 mA 1 Applying KVL to mesh 2 8kI + 4kI + 4k(I – I ) = 0 2 2 2 1 16kI – 4k I = 0 2 1 16kI = 480 2 I = 480/16k 2 I = 30 mA 2 So I will be 0 I =I –I 0 1 2 I = 120 – 30 0 I = 90 mA 0 Example: Calculate the current I and the voltage V . 0 0 Solution: We want to calculate the current I and the voltage V The circuit can be redrawn as 0 0. Applying KVL to mesh 1 2kI +6k(I – I )= 12 1 1 2 8kI – 6kI = 12 1 2 Applying KVL at mesh 2 8kI + 4kI + 6k (I – I ) = 0 2 2 2 1 18kI - 6kI = 0 2 1 Virtual University of Pakistan Page 69 PHY301 – Circuit Theory Solving equations of mesh 1 and mesh 2 24kI - 18kI = 36 1 2 -24kI + 72kI = 0 1 2 54kI = 36 2 I = 36/54k 2 I = 0.67mA ------------(A) 2 Now V will be equal to 0 V = 4k I 0 2 by putting the value of I2 from equation (A) we have V = 2.66 Volts 0 Example: Calculate the current I . 0 Solution: We want to calculate the current I . To apply KVL the circuit can be redrawn as 0 Here I = - 2mA 1 Negative value of I is due to this reason because the direction of I is going opposite to the 1 1 Independent current source. I = 4mA 3 KVL for mesh 2 4kI + 6k (I – I ) + 2k(I – I ) = 12 2 2 3 2 1 12kI – 24 + 4 =12 2 I = 32/12k 2 = 8/3 mA = 2.66 mA I = I = 2.66mA 0 2 Example: Calculate the current I . 0 Virtual University of Pakistan Page 70 PHY301 – Circuit Theory Solution: We want to calculate the current I .The circuit can be redrawn as 0 Here I = - 2mA 1 I = 4mA 3 Apply KVL on the mesh 2 2kI + 1k(I – I ) = 12 2 2 1 3KI + 2 =12 2 I = 10/3 mA 2 I = 3.33mA 2 Now I =I –I 0 1 2 = - 2 – 3.33 I = - 5.33 mA 0 Virtual University of Pakistan Page 71