DC Circuits Lab

1. DC Circuits Lab Professor Ahmadi， Xin Xu ECE 1020

2. Outline • DC and AC circuit • Omh’s Law • Equivalent resistance in series and parallel cuicuits • Exercises & Homework

3. Direct Current (DC) & Alternating Current (AC) • DC: uni-directional movement of electric charges • AC: the direction of the movement of electric charges reverses periodically

4. V I Ohm’s Law • Quantifying the relationship between voltage and current • V voltage, volt (V) • I current, amp (A) • R resistance ohm (Ω) R

5. An Example 3V = Ix 1000 Ω Solve for I: I=3V / 1000 Ω = 3milliAmps I = ? Amps 3V • Determine the current using Ohm’s Law R = 1KΩ

6. V I Resisters in Series Apply Ohm’s Law on each resister R1 Just one path, currents are equal R2 Equivalent resistance Voltage drops can be added up R3

7. V I Principles for Resisters in Series • Current remains same in one circle • Voltage can be added up • Equivalent Resistance equal to sum of all resisters in series R1 R2 R3

8. Examples Online examples for resistances

9. V I Resisters in Parallel Apply Ohm’s Law on each resister R1 R2 R3 Voltages are same on each path Current is divided to 3 paths Equivalent resistance

10. V I Principles for Resisters in Parallel • Voltages remain same in parallel paths • Current can be added up R1 R2 R3

11. Examples Online examples for resistances

12. V V I I Combined Find equivalent resistance for parallel resistances R2 R3 R1 Solve the serial circuit Req R1

13. Examples Online examples for resistances

14. Exercises

15. Exercises – Ohm’s Law • Given a circuit with a power source V = 9V,find the loop current if the resistance is 100 Ohm • Find the loop current by hand, and then build the circuit using the online interactive simulator • What is the current if the resistance is doubled • What is the current if the resistances is reduced by 50% • What is the current if the voltage is doubled? • What is the current if the voltage is reduced by 50%

16. Exercises - series • Given a circuit with a power source V = 12V,find the loop current if resistances are in series • Find the loop current by hand, and then build the circuit using the online interactive simulator • What is the loop current if all resistances are doubled • What is the loop current if all resistances are reduced by 50%

17. V=12V Exercises - parallel • Given a circuit with a power source V = 12V,find the loop current I if 2 resistances are connected in parallel • Find the current I by hand, and then build the circuit using the online interactive simulator • What is the current I if all resistances are doubled? • What is the current I if all resistances are reduced by 50% I = ? R1 R2

18. V Exercises - parallel • Given a circuit with a power source V = 12V,find the loop current if 3 resistances are connected in parallel • Find the current I by hand, and then build the circuit using the online interactive simulator • What is the current I if all resistances are doubled • What is the current I if all resistances are reduced by 50% I = ? R1 R2 R3

19. V Exercises – series/parallel • Given a circuit with a power source V = 5V,find the loop current I if R1, R2 are connected in parallel, and then connected to R3 in series I = ? • Find the current I by hand • Build the circuit using the online interactive simulator to verify your results R1 R2 R3

20. V Exercises – series/parallel • Given a circuit with a power source V = 5V,find the loop current if R1, R2, R3 are connected in parallel, and then connected to R4 in series I = ? • Find the loop current I by hand • Build the circuit using the online interactive simulator to verify your results R1 R2 R3 R4

21. V I = ? Exercises – series/parallel • Find the loop current I by hand, and then build the circuit using the online interactive simulator R4 R3 R1 R2

22. V Homework • Find the loop current I, and voltage and current for each resistor • Build the circuit using the online interactive simulator to verify your results I = ? R4 R3 R1 R2