Lecture # 3 Course Title : Electrical Circuit Analysis 1 ( EEE121 )

1. Lecture # 3 Course Title : Electrical Circuit Analysis 1(EEE121) Course Instructor: Syed Usama Yunas Office: Room – 24, Department of Electrical Engineering Contact email: usamayunas@ciit-attock.edu.pk

2. Simple Resistive Circuits

3. Two elements connected at a single node are actually connected in series. • Elements connected in series have same current. For example, • According to Kirchhoff's current law it can be proved that same current is passing through each node. Therefore, Resistors in Series

4. So if same current say is following through the circuit, we can replace the previous currents with the following, • To find , we will use the Kirchhoff’s voltage law, • All the resistors can be replaced by a single equivalent resistor, so we can write, Resistors in Series(continued…)

5. Combining values will give, Equivalent circuit can be drawn as, • Generally if we have k resistors connected in series. The equivalent resistance can be written as, • Resistance of the equivalent resistor is always larger than the largest resistor in series connection. Resistors in Series(continued…)

6. Two elements connected at a single node pair are actually connected in parallel. • Elements connected in parallel have same voltage across their terminals. For example, • According to Kirchhoff’s current law, • In parallel connection voltage across each resistor will remain the same. So Resistors in Parallel

7. From ohm’s law, • Therefore, • Substituting the above values, Resistors in Parallel(continued…)

8. All the resistors in parallel can be replaced by a single equivalent resistor, so we can write • Equivalent circuit can be drawn as, • Generally if we have k resistors connected in parallel. The equivalent resistance can be written as, • Resistance of the equivalent resistor is always smaller than the smallest resistor in parallel connection. Resistors in Parallel(continued…)

9. In case of two resistors connected in parallel, we have Resistors in Parallel(continued…)

10. Find , and in the following circuit; Example 1

11. Example 2