1. Professor Ahmadi， Xin Xu ECE 1020
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. Ohm’s Law Quantifying the relationship between voltage and current
V voltage, volt (V)
I current, amp (A)
R resistance ohm (Ω) I V R

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

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

7. 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 V R1 I R2 R3

8. Examples
Online examples for resistances

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

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

11. Examples
Online examples for resistances

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

18. 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 = ? V R1 R2 R3

19. 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 V R1 R2 R3

20. 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 V R1 R2 R3 R4

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

22. 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 = ? V R4 R3 R1 R2