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Assignment 1(Fall 2011) (Solution) Circuit Theory (Phy301) Marks: 25 th Due Date: 27 October, 2011 Q.1 Find the equivalent resistance at point a, b of given circuit. Write each step of the calculation to get maximum marks. Draw the circuit diagram of each step otherwise you will lose your marks. Solution: Step 1: 2Ω resistor is in series with 2Ω resistor So 2Ω + 2Ω = 4Ω Step 2: 4Ω resistor is in parallel with 4Ω resistor So 1/R = 1/R + 1/R eq 1 2 = 1/4Ω + 1/4Ω = (4 × 4)/(4 + 4) = 16/8 = 2Ω Step 3: 6Ω Resistor is in series with 2Ω Resistor So 6Ω + 2Ω = 8Ω Step 4: 8Ω resistor is in parallel with 8Ω resistor So 1/Req = 1/R1 + 1/R2 = 1/8Ω + 1/8Ω = (8 × 8)/(8 + 8) = 64/16 = 4Ω Step 5: 5Ω resistor is in series with 4Ω resistor So 5Ω + 4Ω = 9Ω Q.2 Using the division rule, find V and I mentioned in the given circuit. Sol: Finding Current I: As 10Ω resistor is in series with current source therefore current remains same Current will divide at point Node. So current I through 4Ω can be found using current divider formula. R2 2 I *12 A *12 R2 R3 24 2 24 *12 6 6 I 4A So current flow through 4Ω Resistor will be 4A. Now current flow through 2Ω resistor is R3 4 I2 *12 A *12 R3 R 2 42 4 48 *12 8A 6 6 I 2 8A Current flow through 2Ω resistor is 8A. Finding Voltage V: As we know that V = IR So we can find voltage across 2Ω resistor as V = I2 R =8×2 = 16 V Voltage across 2Ω resistor is 16V. Q.3 For the given circuit below, find current flow through each element, for the case when (a) Point a, b is open. (b) Point a, b is closed. Solution: (a) When Point a, b is open As we know that P = V × I So I = P/V = 4/20 = 0.2A So current I1 is 0.2A As point a, b is open therefore current I2 and I3 will be zero (b) When point a, b is closed First we see that all elements are in parallel, so same 20v voltage drops across each element. As we know that P = V × I So I = P/V = 4/20 = 0.2A So current I1 is 0.2A Finding I2 As V = IR I = V/R I2 = 20/5000 I2 = 0.004A So current I2 is 0.004A=4mA Finding I3 As P=VI I = P/V I3 = 10/20 I3 = 0.5A So current I3 is 0.5A

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posted: | 9/12/2012 |

language: | English |

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Past assignments, CS201, CS301, CS304, CS601, Pak301, Eng201, PHY301

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